Trygve Helgaker

Professor - Theoretical chemistry
Image of Trygve Helgaker
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Phone +47 22855428
Mobile phone 95891254
Room V214
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Visiting address Sem Sælands vei 26 0371 Oslo
Postal address Postboks 1033 0315 Oslo
 

Research

Trygve Helgaker works in the area of molecular electronic-structure theory—in particular, on the development and application of methods for quantum-mechanical simulations of molecular systems. With the emergence of powerful computers and the development of sophisticated simulation models and techniques, quantum-chemical simulations have become an indispensable tool for modern chemical research. Such simulations can be performed either as a supplement to experimental work (e.g., for interpretation of experimental data) or as a replacement of experimental investigations (when these cannot be performed or are too expensive).

Even though modern quantum-chemical methods are nowadays successfully applied to a vast range of problems in research and industry, there are still many restrictions with respect to applicability and accuracy. Helgaker's research has been directed towards the development of coupled-cluster theory, density-functional theory, molecular structure and molecular properties, molecular dynamics, and molecules in ultrastrong magnetic fields.

Biography

Trygve Helgaker (born 1953) studied chemistry at the University of Oslo 1975–1980, where he received his master's degree (cand. scient.) in gas-phase electron diffraction in 1980, under the supervision of Prof. Arne Haaland. He visited the electron-diffraction group at Moscow University December 1980 – January 1981.

Helgaker began his PhD studies in theoretical chemistry in 1981 under the supervision of Prof. Jan Almlöf at the University of Oslo, where was awarded the degree of dr. philos. in June 1986. After postdoctoral positions at the Institute for Mathematics and its Applications, University of Minnesota in 1986–87 and at the Department of Chemistry, Aarhus University in 1987–89, he became an assistant professor (førsteamanuensis) in Theoretical Chemistry at the University of Oslo in August 1989. Helgaker became a full professor there in 1993.

Helgaker was on sabbatical leave with Prof. Nicholas Handy at the University of Cambridge 1999–2000 and with Prof. David Tozer at Durham University 2006–2007. He has been guest professor at Laboratoire de Chimie Quantique, Université Louis-Pasteur (ULP), Strasbourg (January 2003) and at Laboratorie de Chimie Théoretique, Université Pierre-et-Marie-Curie (UPMC), Paris (November 2013).

Helgaker has directed two Norwegian Centres of Excellence: Centre for Theoretical and Computational Chemistry from 2013 to 2017 and the Hylleraas Centre for Quantum Molecular Sciences since 2017. In the academic year 2017–2018, he led the project Molecules in Extreme Environments at the Centre for Advanced Study (CAS) at the Norwegian Academy of Science and Letters.

Helgaker studied Russian at the Norwegian Army Language School 1972–1974 and then at the University of Leningrad in 1974–75 and the University of Oslo in 1975. He worked six months as a research assistant for Prof.Geir Kjetsaa on the project Written by Dostoevsky? during 1979 and as a teacher in Russian syntax in the spring term of 1980, both at the Department of Slavic and Baltic Studies, University of Oslo.

Publications

Helgaker has authored 356 publications with 26000 citations and H-index 76 on Web of Science and with 37000 citations and H-index 89 on GoogleScholar. All publications allowed by copyright can be downloaded from the publication list.

Together with Poul Jørgensen and Jeppe Olsen at Aarhus University, Helgaker has written the monograph Molecular Electronic-Structure Theory (Wiley, Chichster, 2000), which has been cited more than 3600 times in the literature.

Helgaker has translated Russian fiction to Norwegian: Leo Tolstoy, Om vold og kjærlighet (Solum, Oslo, 1977) and Boris Pilnyak, Armesjefens død, in Moderne russiske fortellere, ed. G. Kjetsaa (Aschehoug, Oslo, 1977).

Talks

Helgaker has given more than 400 scientific talks at seminars, meetings, conferences, and summer schools. The slides of most of these talks can be downloaded .

Teaching and Supervision

Helgaker taught course in physical and theoretical chemistry at the University of Oslo from 1989 to 2012. In addition, Helgaker has taught 13 times at the Sostrup Summer School of Quantum Chemistry and Molecular Properties (organized with P. Jørgensen and J. Olsen) from 1990 to 2014 and 16 times at the European Summerschool of Quantum Chemistry (ESQC) from 1991 to 2019, giving a total of 170 lectures at these schools. He has also taught at the Helsinki Winter School in Theoretical Chemistry (1991, 2000, 2010) and at the summer school Modern Wavefunction Methods (MWM) in Electronic Structure Theory (2016,2018) in Gelsenkirchen, Germany. Lectures given at these schools can be downloaded from Presentations.

Slides for KJM2600—Quantum Chemistry and Spectroscopy can be downloaded.

Helgaker has supervised 16 master students, 12 PhD students, and 19 postdocs.

Events Organized

Helgaker has organized and co-organized 22 scienfitic workshops, meetings, and conferences. In addition, the Sostrup Summer School of Quantum Chemistry and Molecular Properties was held 13 times from 1990 to 1999, organized together with Poul Jørgensen and Jeppe Olsen.

Funding and Grants

Helgaker has received grants and financial support for several projects, including an Advanced Grant from the European Research Council and two grants for Centre of Excellence (Senter for fremragende forskning) from the Norwegian Research Council.

Boards and Committees

Helgaker is the member of a number of boards and committees, including services for several journals. He has been an editor of Molecular Physics since 2013.

Software Development

Since the 1980s, Trygve Helgaker has developed the Dalton quantum chemistry program system in collaboration with other researchers in Scandinavia—important contributions being molecular-integral evaluation, geometric and magnetic molecular properties, geometry optimizations, molecular dynamics, and density-functional theory.

His molecular-integral codes Hermit, ERI and ABACUS, which form part of Dalton, have also been incorporated into several other quantum-chemistry codes, including ACES, Columbus, Dirac, and ENDyne.

Awards and Honours

Helgaker has received a number of awards and honours, including the University of Oslo Research Prize (2006), the Centenary Prize of the Royal Society of Chemistry (2007), the Guldberg–Waage Medal of the Norwegian Chemical Society (2007), the Award for Outstanding Research (Møbius Prize) of the Research Council of Norway (2011), and the Fridtjov Nansen Award for Excellence in Science of the Norwegian Academy of Science and Letters (2019).

Helgaker is an elected member of the Norwegian Academy of Science and Letters (2004) and the Royal Swedish Academy of Sciences (2021). He is a member for the Norwegian Chemical Society and an elected member of the International Academy of Quantum Molecular Science (2005).

Collaborations


  • Jürgen Gauss, University of Mainz, Germany
  • Simen Kvaal, University of Oslo, Norway
  • Michal Jaszunski, Polish Acad. Sciences, Warsaw, Poland
  • Hans-Jørgen Aa. Jensen, University of Southern Denmark
  • Poul Jørgensen, Aarhus University, Denmark
  • André Laestadius, University of Oslo, Norway
  • Jeppe Olsen, Aarhus University, Denmark
  • Thomas Bondo Pedersen, University of Oslo, Norway
  • Kenneth Ruud, UiT The Arctic University of Norway
  • Trond Saue, Université Paul Sabatier, Toulouse, France
  • Andreas Savin, Sorbonne Université, Paris, France
  • Peter Schwerdtfeger, Massey University, New Zealand
  • Stella Stopkowicz, University of Mainz, Germany
  • Dage Sundholm, Helsinki University, Finland
  • Peter Taylor, Tianjin University, China
  • Erik Tellgren, University of Oslo, Norway
  • Andrew Teale, University of Nottingham, UK
  • Einar Uggerud, University of Oslo, Norway

CV

Tags: theoretical chemistry, electronic-structure theory, computational chemistry, molecular properties

Publications

All publications can be downloaded here when permitted by copyright agreement.

  • Culpitt, Tanner Phillip; Peters, Laurens; Tellgren, Erik Ingemar & Helgaker, Trygve (2022). Analytic calculation of the Berry curvature and diagonal Born-Oppenheimer correction for molecular systems in uniform magnetic fields. Journal of Chemical Physics. ISSN 0021-9606. 156(4). doi: 10.1063/5.0079304. Full text in Research Archive
  • Dembiński, Stanisław; Karwowski, Jacek; Szudy, Józef & Helgaker, Trygve (2022). Lutosław Wolniewicz (1930–2020). Molecular Physics. ISSN 0026-8976. doi: 10.1080/00268976.2021.2024904.
  • Kvaal, Simen; Laestadius, Andre; Tellgren, Erik Ingemar & Helgaker, Trygve (2021). Lower Semicontinuity of the Universal Functional in Paramagnetic Current-Density Functional Theory. The Journal of Physical Chemistry Letters. ISSN 1948-7185. 12(5), p. 1421–1425. doi: 10.1021/acs.jpclett.0c03422. Full text in Research Archive
  • Peters, Laurens; Culpitt, Tanner Phillip; Monzel, Laurenz; Tellgren, Erik Ingemar & Helgaker, Trygve (2021). Ab Initio molecular dynamics with screened Lorentz forces. II. Efficient propagators and rovibrational spectra in strong magnetic fields. Journal of Chemical Physics. ISSN 0021-9606. 155. doi: 10.1063/5.0056235.
  • Culpitt, Tanner Phillip; Peters, Laurens; Tellgren, Erik Ingemar & Helgaker, Trygve (2021). Ab initio molecular dynamics with screened Lorentz forces. I. Calculation and atomic charge interpretation of Berry curvature . Journal of Chemical Physics. ISSN 0021-9606. 155(2). doi: 10.1063/5.0055388. Full text in Research Archive
  • Ryley, Matthew S.; Withnall, Michael; Irons, Tom J. P.; Helgaker, Trygve & Teale, Andrew Michael (2021). Robust All-Electron Optimization in Orbital-Free Density-Functional Theory Using the Trust-Region Image Method. Journal of Physical Chemistry A. ISSN 1089-5639. 125(1), p. 459–475. doi: 10.1021/acs.jpca.0c09502.
  • Brandenburg, Jan Gerit; Burke, Kieron; Fromager, Emmanuel; Gatti, Matteo; Giarrusso, Sara & Gidopoulos, Nikitas I. [Show all 29 contributors for this article] (2020). New approaches to study excited states in density functional theory: general discussion. Faraday discussions. ISSN 1359-6640. 224, p. 483–508. doi: 10.1039/D0FD90026E.
  • Fromager, Emmanuel; Gidopoulos, Nikitas I.; Gori-Giorgi, Paola; Helgaker, Trygve; Loos, Pierre-François & Malcomson, Thomas [Show all 11 contributors for this article] (2020). Strong correlation in density functional theory: general discussion. Faraday discussions. ISSN 1359-6640. 224, p. 373–381. doi: 10.1039/D0FD90025G.
  • Brandenburg, Jan Gerit; Burke, Kieron; Civalleri, Bartolomeo; Cole, Daniel J.; Csanyi, Gabor & Gregoire, David [Show all 27 contributors for this article] (2020). Challenges for large scale simulation: general discussion. Faraday discussions. ISSN 1359-6640. 224, p. 309–332. doi: 10.1039/D0FD90024A.
  • Brandenburg, Jan Gerit; Burke, Kieron; Cancio, Antonio; Erhard, Jannis; Fromager, Emmanuel & Ghosal, Abhisek [Show all 25 contributors for this article] (2020). New density-functional approximations and beyond: general discussion. Faraday discussions. ISSN 1359-6640. 224, p. 166–200. doi: 10.1039/D0FD90023K.
  • Austad, Jon; Borgoo, Alex; Tellgren, Erik & Helgaker, Trygve (2020). Bonding in the helium dimer in strong magnetic fields: The role of spin and angular momentum. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 22(41), p. 23502–23521. doi: 10.1039/d0cp03259j.
  • Castro, Abril C; Balcells, David; Repisky, Michal; Helgaker, Trygve & Cascella, Michele (2020). First-principles calculation of 1H NMR chemical shifts of complex metal polyhydrides: The essential inclusion of relativity and dynamics. Inorganic Chemistry. ISSN 0020-1669. 59(23), p. 17509–17518. doi: 10.1021/acs.inorgchem.0c02753. Full text in Research Archive
  • Adamowicz, Ludwik; Stanke, Monika; Tellgren, Erik & Helgaker, Trygve (2020). A quantum-mechanical non-Born–Oppenheimer model of a molecule in a strong magnetic field. Chemical Physics Letters. ISSN 0009-2614. 761, p. 1–7. doi: 10.1016/j.cplett.2020.138041. Full text in Research Archive
  • Irons, Tom J P; Spence, Lucy; Speake, Gregoire David; Speake, Benjamin T.; Helgaker, Trygve & Teale, Andrew Michael (2020). Analyzing Magnetically Induced Currents in Molecular Systems Using Current-Density-Functional Theory. Journal of Physical Chemistry A. ISSN 1089-5639. 124, p. 1321–1333. doi: 10.1021/acs.jpca.9b10833.
  • Olsen, Jógvan Magnus Haugaard; Reine, Simen Sommerfelt; Vahtras, Olav; Kjellgren, Erik; Reinholdt, Peter & Dundas, Karen O.H [Show all 25 contributors for this article] (2020). Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems. Journal of Chemical Physics. ISSN 0021-9606. 152(21). doi: 10.1063/1.5144298. Full text in Research Archive
  • Pasteka, Lukáš Félix; Helgaker, Trygve; Saue, Trond; Sundholm, Dage; Werner, Hans-Joachim & Hasanbulli, Mustafa [Show all 8 contributors for this article] (2020). Atoms and molecules in soft confinement potentials. Molecular Physics. ISSN 0026-8976. p. 1–23. doi: 10.1080/00268976.2020.1730989.
  • Laestadius, Andre; Tellgren, Erik; Penz, Markus; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2019). Kohn–Sham Theory with Paramagnetic Currents: Compatibility and Functional Differentiability. Journal of Chemical Theory and Computation. ISSN 1549-9618. 15(7), p. 4003–4020. doi: 10.1021/acs.jctc.9b00141.
  • Holzer, Christof; Teale, Andrew Michael; Hampe, Florian; Stopkowicz, Stella; Helgaker, Trygve & Klopper, Wim (2019). GW quasiparticle energies of atoms in strong magnetic fields. Journal of Chemical Physics. ISSN 0021-9606. 150(21), p. 214112-1–214112-9. doi: 10.1063/1.5093396.
  • Castro, Abril C.; Fliegl, Heike; Cascella, Michele; Helgaker, Trygve; Repisky, Michal & Komorovsky, Stanislav [Show all 9 contributors for this article] (2019). Four-component relativistic 31P NMR calculations for: Trans -platinum(ii) complexes: Importance of the solvent and dynamics in spectral simulations. Dalton Transactions. ISSN 1477-9226. 48(23), p. 8076–8083. doi: 10.1039/c9dt00570f. Full text in Research Archive
  • Reimann, Sarah; Borgoo, Alex; Austad, Jon; Tellgren, Erik; Teale, Andrew Michael & Helgaker, Trygve (2019). Kohn–Sham energy decomposition for molecules in a magnetic field. Molecular Physics. ISSN 0026-8976. 117(1), p. 97–109. doi: 10.1080/00268976.2018.1495849.
  • Adamowicz, Ludwik; Stanke, Monika; Tellgren, Erik & Helgaker, Trygve (2018). A computational quantum-mechanical model of a molecular magnetic trap. Journal of Chemical Physics. ISSN 0021-9606. 149(24), p. 244112-1–244112-11. doi: 10.1063/1.5055767.
  • Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2018). Generalized Kohn-Sham iteration on Banach spaces. Journal of Chemical Physics. ISSN 0021-9606. 149(16), p. 1–9. doi: 10.1063/1.5037790. Full text in Research Archive
  • Holzer, Christof; Gui, Xin; Harding, Michael E.; Kresse, Georg; Helgaker, Trygve & Klopper, Wim (2018). Bethe-Salpeter correlation energies of atoms and molecules. Journal of Chemical Physics. ISSN 0021-9606. 149(14), p. 144106-1–144106-9. doi: 10.1063/1.5047030.
  • Rebolini, Elisa; Teale, Andrew Michael; Helgaker, Trygve; Savin, Andreas & Toulouse, Julien (2018). Excitation energies from Gorling?Levy perturbation theory along the range-separated adiabatic connection. Molecular Physics. ISSN 0026-8976. 116(11), p. 1443–1451. doi: 10.1080/00268976.2017.1422811.
  • Tellgren, Erik; Laestadius, Andre; Helgaker, Trygve; Kvaal, Simen & Teale, Andrew Michael (2018). Uniform magnetic fields in density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 148(2), p. 1–19. doi: 10.1063/1.5007300.
  • Irons, Tom J P; Furness, James W.; Ryley, Matthew S.; Zemen, Jan; Helgaker, Trygve & Teale, Andrew Michael (2017). Connections between variation principles at the interface of wave-function and density-functional theories. Journal of Chemical Physics. ISSN 0021-9606. 147(13). doi: 10.1063/1.4985883. Full text in Research Archive
  • Reimann, Sarah; Borgoo, Alex; Tellgren, Erik; Teale, Andrew Michael & Helgaker, Trygve (2017). Magnetic-Field Density-Functional Theory (BDFT): Lessons from the Adiabatic Connection. Journal of Chemical Theory and Computation. ISSN 1549-9618. 13(9), p. 4089–4100. doi: 10.1021/acs.jctc.7b00295. Full text in Research Archive
  • Adamowicz, Ludwik; Stanke, Monika; Tellgren, Erik & Helgaker, Trygve (2017). Explicitly-correlated non-born-oppenheimer calculations of the HD molecule in a strong magnetic field. Chemical Physics Letters. ISSN 0009-2614. 682, p. 87–90. doi: 10.1016/j.cplett.2017.06.016.
  • Kumar, Chandan; Kjærgaard, Thomas; Helgaker, Trygve & Fliegl, Heike (2016). Nuclei-selected atomic orbital response theory formulation of NMR shielding tensors using density-fitting. Journal of Chemical Physics. ISSN 0021-9606. 145(23), p. 1–10. doi: 10.1063/1.4972212.
  • Helgaker, Trygve; Jaszunski, Michal & Swider, Pawel (2016). Calculation of NMR Spin-Spin Coupling Constants in Strychnine. Journal of Organic Chemistry. ISSN 0022-3263. 81(22), p. 11496–11500. doi: 10.1021/acs.joc.6b02157.
  • Rebolini, Elisa; Izsak, Robert; Reine, Simen Sommerfelt; Helgaker, Trygve & Pedersen, Thomas Bondo (2016). Comparison of Three Efficient Approximate Exact-Exchange Algorithms: The Chain-of-Spheres Algorithm, Pair-Atomic Resolution-of-the-Identity Method, and Auxiliary Density Matrix Method. Journal of Chemical Theory and Computation. ISSN 1549-9618. 12, p. 3514–3522. doi: 10.1021/acs.jctc.6b00074.
  • Furness, James W.; Ekström, Ulf Egil; Helgaker, Trygve & Teale, Andrew Michael (2016). Electron localisation function in current-density-functional theory. Molecular Physics. ISSN 0026-8976. 114(7-8), p. 1415–1422. doi: 10.1080/00268976.2015.1133859.
  • Teale, Andrew Michael; Helgaker, Trygve & Savin, Andreas (2016). Alternative Representations of the Correlation Energy in Density-Functional Theory: A Kinetic-Energy Based Adiabatic Connection. Journal of the Chinese Chemical Society (Taipei). ISSN 0009-4536. 63(1), p. 121–128. doi: 10.1002/jccs.201500132.
  • Borgoo, Alex; Teale, Andrew Michael & Helgaker, Trygve (2015). Excitation energies from ensemble DFT. AIP Conference Proceedings. ISSN 0094-243X. 1702:090049. doi: 10.1063/1.4938857.
  • Kvaal, Simen & Helgaker, Trygve (2015). Ground-state densities from the Rayleigh-Ritz variation principle and from density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 143(18). doi: 10.1063/1.4934797.
  • Peach, Michael J. G.; Teale, Andrew Michael; Helgaker, Trygve & Tozer, David J. (2015). Fractional electron loss in approximate DFT and Hartree-Fock theory. Journal of Chemical Theory and Computation. ISSN 1549-9618. 11(11), p. 5262–5268. doi: 10.1021/acs.jctc.5b00804.
  • Adamowicz, Ludwik; Tellgren, Erik & Helgaker, Trygve (2015). Non-Born-Oppenheimer calculations of the HD molecule in a strong magnetic field. Chemical Physics Letters. ISSN 0009-2614. 639, p. 295–299. doi: 10.1016/j.cplett.2015.09.051.
  • Furness, James W.; Verbeke, Joachim; Tellgren, Erik; Stopkowicz, Stella; Ekström, Ulf Egil & Helgaker, Trygve [Show all 7 contributors for this article] (2015). Current density functional theory using meta-generalized gradient exchange-correlation functionals. Journal of Chemical Theory and Computation. ISSN 1549-9618. 11(9), p. 4169–4181. doi: 10.1021/acs.jctc.5b00535.
  • Stopkowicz, Stella; Gauss, Jürgen; Lange, Kai Kaarvann; Tellgren, Erik & Helgaker, Trygve (2015). Coupled-cluster theory for atoms and molecules in strong magnetic fields. Journal of Chemical Physics. ISSN 0021-9606. 143:074110(7). doi: 10.1063/1.4928056.
  • Reimann, Sarah; Ekström, Ulf Egil; Stopkowicz, Stella; Teale, Andrew Michael; Borgoo, Alex & Helgaker, Trygve (2015). The importance of current contributions to shielding constants in density-functional theory. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 17(28), p. 18834–18842. doi: 10.1039/c5cp02682b.
  • Cheng, Chi Y.; Ryley, Matthew S.; Peach, Michael J.G.; Tozer, David J.; Helgaker, Trygve & Teale, Andrew Michael (2015). Molecular properties in the Tamm–Dancoff approximation: indirect nuclear spin–spin coupling constants. Molecular Physics. ISSN 0026-8976. 113(13-14), p. 1937–1951. doi: 10.1080/00268976.2015.1024182.
  • Ryding, Mauritz Johan Olof; Izsak, Robert; Merlot, Patrick; Reine, Simen Sommerfelt; Helgaker, Trygve & Uggerud, Einar (2015). Geometry of the magic number H+(H2O)21 water cluster by proxy. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 17, p. 5466–5473. doi: 10.1039/C4CP05246C.
  • Rebolini, Elisa; Toulouse, Julien; Teale, Andrew Michael; Helgaker, Trygve & Savin, A (2015). Calculating excitation energies by extrapolation along adiabatic connections. Physical Review A. Atomic, Molecular, and Optical Physics (PRA). ISSN 1050-2947. 91. doi: 10.1103/PhysRevA.91.032519. Full text in Research Archive
  • Hoffmann, Mark R. & Helgaker, Trygve (2015). Use of Density Functional Theory Orbitals in the GVVPT2 Variant of Second-Order Multistate Multireference Perturbation Theory. Journal of Physical Chemistry A. ISSN 1089-5639. 119, p. 1548–1553. doi: 10.1021/jp507554v.
  • Rebolini, Elisa; Toulouse, Julien; Teale, Andrew Michael; Helgaker, Trygve & Savin, Andreas (2015). Excited states from a range-separated density-functional perturbation theory. Molecular Physics. ISSN 0026-8976. 113(13-14), p. 1740–1749. doi: 10.1080/00268976.2015.1011248.
  • Merlot, Patrick; Izsak, Robert; Borgoo, Alex; Kjærgaard, Thomas; Helgaker, Trygve & Reine, Simen Sommerfelt (2014). Charge-constrained auxiliary-density-matrix methods for the Hartree-Fock exchange contribution. Journal of Chemical Physics. ISSN 0021-9606. 141(9). doi: 10.1063/1.4894267.
  • Smalø, Hans Sverre; Rybkin, Vladimir; Klopper, Wim; Helgaker, Trygve & Uggerud, Einar (2014). Mechanochemistry: The effect of dynamics. Journal of Physical Chemistry A. ISSN 1089-5639. 118(36), p. 7683–7694. doi: 10.1021/jp504959z.
  • Rebolini, Elisa; Toulouse, Julien; Teale, Andrew Michael; Helgaker, Trygve & Savin, Andreas (2014). Excitation energies along a range-separated adiabatic connection. Journal of Chemical Physics. ISSN 0021-9606. 141(4). doi: 10.1063/1.4890652.
  • Tellgren, Erik; Teale, Andrew Michael; Furness, J.W.; Lange, Kai Kaarvann; Ekström, Ulf Egil & Helgaker, Trygve (2014). Non-perturbative calculation of molecular magnetic properties within current-density functional theory. Journal of Chemical Physics. ISSN 0021-9606. 140(3). doi: 10.1063/1.4861427.
  • Ringholm, Magnus; Jonsson, Dan Johan; Bast, Radovan; Gao, Bin; Thorvaldsen, Andreas johan & Ekstrøm, Ulf [Show all 8 contributors for this article] (2014). Analytic cubic and quartic force fields using density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 140(3). doi: 10.1063/1.4861003. Full text in Research Archive
  • Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2014). Differentiable but exact formulation of density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 140(18). doi: 10.1063/1.4867005.
  • Tellgren, Erik; Kvaal, Simen & Helgaker, Trygve (2014). Fermion N -representability for prescribed density and paramagnetic current density. Physical Review A. Atomic, Molecular, and Optical Physics (PRA). ISSN 1050-2947. 89(1). doi: 10.1103/PhysRevA.89.012515. Full text in Research Archive
  • Aidas, Kestutis; Angeli, Celestino; Bak, Keld L.; Bakken, Vebjørn; Bast, Radovan & Boman, Linus [Show all 83 contributors for this article] (2014). The Dalton quantum chemistry program system. Wiley Interdisciplinary Reviews. Computational Molecular Science. ISSN 1759-0876. 4(3), p. 269–284. doi: 10.1002/wcms.1172. Full text in Research Archive
  • Onishi, Taku & Helgaker, Trygve (2013). A Theoretical Study on Hydrogen Transport Mechanism in SrTio(3) Perovskite. International Journal of Quantum Chemistry. ISSN 0020-7608. 112(1), p. 201–207. doi: 10.1002/qua.23203.
  • Onishi, Taku & Helgaker, Trygve (2013). A Theoretical Study on the Hydrogen Transport Mechanism in SrTiO 3 Perovskite. II. Scandium Doping at Titanium Site . International Journal of Quantum Chemistry. ISSN 0020-7608. 113, p. 599–604. doi: 10.1002/qua.24086.
  • Helgaker, Trygve; Gauss, Jürgen; Gabriele, Cazzoli & Cristina, Puzzarini (2013). 33S hyperfine interactions in H2S and SO2 and revision of the sulfur nuclear magnetic shielding scale. Journal of Chemical Physics. ISSN 0021-9606. 139(24:244308). doi: 10.1063/1.4849177.
  • Onishi, Taku & Helgaker, Trygve (2013). A Theoretical Study on Proton Conduction Mechanism in BaZrO3 Perovskite. In Hotokka, Matti; Brändas, Erkki J.; Maruani, Jean & Delgado-Barrio, Gerardo (Ed.), Advances in Quantum Methods and Applications in Chemistry, Physics, and Biology. Springer. ISSN 978-3-319-01528-6. p. 238–248. doi: 10.1007/978-3-319-01529-3_14.
  • Stoyanova, Alexandrina; Teale, Andrew Michael; Toulouse, Julien; Helgaker, Trygve & Fromager, Emmanuel (2013). Alternative separation of exchange and correlation energies in multi-configuration range-separated density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 139(13). doi: 10.1063/1.4822135.
  • Rekkedal, Johannes Andreas; Coriani, Sonia; Iozzi, Maria Francesca; Teale, Andrew Michael; Helgaker, Trygve & Pedersen, Thomas Bondo (2013). Communication: Analytic gradients in the random-phase approximation. Journal of Chemical Physics. ISSN 0021-9606. 139(8). doi: 10.1063/1.4819399.
  • Przybytek, Michal & Helgaker, Trygve (2013). The accuracy of the Gaussian-and-finite-element-Coulomb (GFC) method for the calculation of Coulomb integrals. Journal of Chemical Physics. ISSN 0021-9606. 139(5). doi: 10.1063/1.4817002.
  • Rybkin, Vladimir; Ekstrøm, Ulf & Helgaker, Trygve (2013). Internal-to-Cartesian Back Transformation of Molecular Geometry Steps Using High-Order Geometric Derivatives. Journal of Computational Chemistry. ISSN 0192-8651. 34, p. 1842–1849. doi: 10.1002/jcc.23327.
  • Merlot, Patrick; Kjærgaard, Thomas; Helgaker, Trygve; Lindh, Roland; Aquilante, Francesco & Reine, Simen Sommerfelt [Show all 7 contributors for this article] (2013). Attractive electron-electron interactions within robust local fitting approximations. Journal of Computational Chemistry. ISSN 0192-8651. 34(17), p. 1486–1496. doi: 10.1002/jcc.23284.
  • Rybkin, Vladimir; Simakov, Anton; Bakken, Vebjørn; Reine, Simen Sommerfelt; Kjærgaard, Thomas & Helgaker, Trygve [Show all 7 contributors for this article] (2013). Insights into the dynamics of evaporation and proton migration in protonated water clusters from large-scale bornoppenheimer direct dynamics. Journal of Computational Chemistry. ISSN 0192-8651. 34(7), p. 533–544. doi: 10.1002/jcc.23162.
  • Teale, Andrew Michael; Lutnæs, Ola Berg; Helgaker, Trygve; Tozer, David J. & Gauss, Jürgen (2013). Benchmarking density-functional theory calculations of NMR shielding constants and spin-rotation constants using accurate coupled-cluster calculations. Journal of Chemical Physics. ISSN 0021-9606. 138(2). doi: 10.1063/1.4773016.
  • Helgaker, Trygve; Jaszunski, Michal; Garbacz, Piotr & Jackowski, Karol (2012). The NMR indirect nuclear spin-spin coupling constant of the HD molecule. Molecular Physics. ISSN 0026-8976. 110(19-20), p. 2611–2617. doi: 10.1080/00268976.2012.729097.
  • Middendorf, Nils; Höfener, Sebastian; Klopper, Wim & Helgaker, Trygve (2012). Calculation of the two-electron Darwin term using explicitly correlated wave functions. Chemical Physics. ISSN 0301-0104. 401, p. 146–151. doi: 10.1016/j.chemphys.2011.10.035.
  • Tellgren, Erik; Reine, Simen Sommerfelt & Helgaker, Trygve (2012). Analytical GIAO and hybrid-basis integral derivatives: application to geometry optimization of molecules in strong magnetic fields. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 14(26), p. 9492–9499. doi: 10.1039/c2cp40965h.
  • Kaarvann, Lange Kai; Tellgren, Erik; Hoffmann, Mark & Helgaker, Trygve (2012). A Paramagnetic Bonding Mechanism for Diatomics in Strong Magnetic Fields. Science. ISSN 0036-8075. 337(6092), p. 327–331. doi: 10.1126/science.1219703.
  • Reine, Simen Sommerfelt; Helgaker, Trygve & Lindh, Roland (2012). Multi-electron integrals. Wiley Interdisciplinary Reviews. Computational Molecular Science. ISSN 1759-0876. 2(2), p. 290–303. doi: 10.1002/wcms.78.
  • Helgaker, Trygve; Coriani, Sonia; Jørgensen, Poul; Kristensen, Kasper; Olsen, Jeppe & Ruud, Kenneth (2012). Recent Advances in Wave Function-Based Methods of Molecular-Property Calculations. Chemical Reviews. ISSN 0009-2665. 112(1), p. 543–631. doi: 10.1021/cr2002239.
  • Onishi, Taku & Helgaker, Trygve (2012). A Theoretical Study on Hydrogen Transport Mechanism in SrTio(3) Perovskite. International Journal of Quantum Chemistry. ISSN 0020-7608. 112(1), p. 201–207. doi: 10.1002/qua.23203.
  • Teale, Andrew Michael; Coriani, Sonia & Helgaker, Trygve (2012). Range-dependent adiabatic connections. AIP Conference Proceedings. ISSN 0094-243X. 1504, p. 92–99. doi: 10.1063/1.4771706. Full text in Research Archive
  • Tellgren, Erik; Kvaal, Simen; Sagvolden, Espen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2012). Choice of basic variables in current-density-functional theory. Physical Review A. Atomic, Molecular, and Optical Physics (PRA). ISSN 1050-2947. 86(6). doi: 10.1103/PhysRevA.86.062506. Full text in Research Archive
  • Strømsheim, Marie Døvre; Kumar, Neena Theresa; Coriani, Sonia; Sagvolden, Espen; Teale, Andrew Michael & Helgaker, Trygve (2011). Dispersion interactions in density-functional theory: An adiabatic-connection analysis. Journal of Chemical Physics. ISSN 0021-9606. 135(19). doi: 10.1063/1.3660357.
  • Bast, Radovan; Ruud, Kenneth; Rizzo, Antonio & Helgaker, Trygve (2011). Relativistic four-component calculations of Buckingham birefringence using London atomic orbitals. Theoretical Chemistry Accounts. ISSN 1432-881X. 129(3-5), p. 685–699. doi: 10.1007/s00214-011-0939-3. Full text in Research Archive
  • Klopper, Wim; Teale, Andrew Michael; Coriani, Sonia; Pedersen, Thomas Bondo & Helgaker, Trygve (2011). Spin flipping in ring-coupled-cluster-doubles theory. Chemical Physics Letters. ISSN 0009-2614. 510(1-3), p. 147–153. doi: 10.1016/j.cplett.2011.04.101.
  • Iozzi, Maria Francesca; Helgaker, Trygve & Uggerud, Einar (2011). Influence of External Force on Properties and Reactivity of Disulfide Bonds. Journal of Physical Chemistry A. ISSN 1089-5639. 115(11), p. 2308–2315. doi: 10.1021/jp109428g.
  • Bast, Radovan; Ulf, Ekstrom; Gao, Bin; Helgaker, Trygve; Ruud, Kenneth & Thorvaldsen, Andreas johan (2011). The ab initio calculation of molecular electric, magnetic and geometric properties. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 13(7), p. 2627–2651. doi: 10.1039/c0cp01647k.
  • Teale, Andrew Michael; Coriani, Sonia & Helgaker, Trygve (2010). Range-dependent adiabatic connections. Journal of Chemical Physics. ISSN 0021-9606. 133(16). doi: 10.1063/1.3488100.
  • Lutnæs, Ola Berg; Helgaker, Trygve & Jaszunski, Michal (2010). Spin-spin coupling constants and triplet instabilities in Kohn-Sham theory. Molecular Physics. ISSN 0026-8976. 108(19-20), p. 2579–2590. doi: 10.1080/00268976.2010.513344.
  • Teale, Andrew Michael; Coriani, Sonia & Helgaker, Trygve (2010). Accurate calculation and modeling of the adiabatic connection in density functional theory. Journal of Chemical Physics. ISSN 0021-9606. 132(16). doi: 10.1063/1.3380834.
  • Reine, Simen Sommerfelt; Krapp, Andreas; Iozzi, Maria Francesca; Bakken, Vebjørn; Helgaker, Trygve & Pawlowski, Filip [Show all 7 contributors for this article] (2010). An efficient density-functional-theory force evaluation for large molecular systems. Journal of Chemical Physics. ISSN 0021-9606. 133(4). doi: 10.1063/1.3459061.
  • Lutnæs, Ola B.; Teale, AM; Helgaker, Trygve; Tozer, DJ; Ruud, Kenneth & Gauss, J (2009). Benchmarking density-functional-theory calculations of rotational g tensors and magnetizabilities using accurate coupled-cluster calculations. Journal of Chemical Physics. ISSN 0021-9606. 131(14). doi: 10.1063/1.3242081.
  • Teale, Andrew Michael; Coriani, Sonia & Helgaker, Trygve (2009). The calculation of adiabatic-connection curves from full configuration-interaction densities: Two-electron systems. Journal of Chemical Physics. ISSN 0021-9606. 130(10). doi: 10.1063/1.3082285.
  • Hofener, S; Tew, DP; Klopper, W & Helgaker, Trygve (2009). The geminal basis in explicitly correlated wave functions. Chemical Physics. ISSN 0301-0104. 356(1-3), p. 25–30. doi: 10.1016/j.chemphys.2008.10.022.
  • Friedrich, Joachim; Coriani, Sonia; Helgaker, Trygve & Dolg, Michael (2009). Implementation of the incremental scheme for one-electron first-order properties in coupled-cluster theory. Journal of Chemical Physics. ISSN 0021-9606. 131(15). doi: 10.1063/1.3243864.
  • Iozzi, Maria Francesca; Helgaker, Trygve & Uggerud, Einar (2009). Assessment of theoretical methods for the determination of the mechanochemical strength of covalent bonds. Molecular Physics. ISSN 0026-8976. 107(23-24), p. 2537–2546. doi: 10.1080/00268970903401041.
  • Tellgren, Erik; Helgaker, Trygve & Soncini, Alessandro (2009). Non-perturbative magnetic phenomena in closed-shell paramagnetic molecules. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 11(26), p. 5489–5498. doi: 10.1039/b822262b.
  • Jansik, B; Host, S; Johansson, MP; Olsen, J; Jorgensen, P & Helgaker, Trygve (2009). A stepwise atomic, valence-molecular, and full-molecular optimisation of the Hartree-Fock/Kohn-Sham energy. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 11(27), p. 5805–5813. doi: 10.1039/b901987a.
  • Jansik, Branislav; Høst, Stinne; Johansson, M. P.; Olsen, Jeppe; Jørgensen, Poul & Helgaker, Trygve (2009). Robust and Reliable Multilevel Minimization of the Kohn-Sham Energy. Journal of Chemical Theory and Computation. ISSN 1549-9618. 5(4), p. 1027–1032. doi: 10.1021/ct800562h.
  • Helgaker, Trygve; Jaszunski, Michal & Pecul, Magdalena (2008). The quantum-chemical calculation of NMR indirect spin-spin coupling constants. Progress in nuclear magnetic resonance spectroscopy. ISSN 0079-6565. 53, p. 249–268.
  • Helgaker, Trygve; Klopper, Wim & Tew, David P. (2008). Quantitative quantum chemistry. Molecular Physics. ISSN 0026-8976. 106, p. 2107–2143.
  • Bast, Radovan; Hesselmann, Andreas; Salek, Pawel; Helgaker, Trygve & Saue, Trond (2008). Static and Frequency-Dependent Dipole–Dipole Polarizabilities of All Closed-Shell Atoms up to Radium: A Four-Component Relativistic DFT Study. ChemPhysChem. ISSN 1439-4235. 9(3), p. 445–53. doi: 10.1002/cphc.200700504.
  • Peach, Michael J. G.; Benfield, Peter; Helgaker, Trygve & Tozer, David J. (2008). Excitation energies in density functional theory: An evaluation and a diagnostic test. Journal of Chemical Physics. ISSN 0021-9606. 128. doi: 10.1063/1.2831900.
  • Host, S; Jansik, B; Olsen, J; Jorgensen, P; Reine, Simen Sommerfelt & Helgaker, Trygve (2008). A ground-state-directed optimization scheme for the Kohn-Sham energy. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 10, p. 5344–5348. doi: 10.1039/b807639a.
  • Kiaergaard, T; Jorgensen, P; Olsen, J; Coriani, Sonia & Helgaker, Trygve (2008). Hartree-Fock and Kohn-Sham time-dependent response theory in a second-quantization atomic-orbital formalism suitable for linear scaling. Journal of Chemical Physics. ISSN 0021-9606. 129. doi: 10.1063/1.2961039.
  • Soncini, Alessandro; Teale, Andrew Michael; Helgaker, Trygve; De Proft, F & Tozer, DJ (2008). Maps of current density using density-functional methods. Journal of Chemical Physics. ISSN 0021-9606. 129. doi: 10.1063/1.2969104.
  • Tellgren , Erik I; Soncini, Alessandro & Helgaker, Trygve (2008). Nonperturbative ab initio calculations in strong magnetic fields using London orbitals. Journal of Chemical Physics. ISSN 0021-9606. 129, p. 154114-1–154114-9.
  • Reine, Simen Sommerfelt; Tellgren, Erik; Krapp, Andreas; Kjærgaard, Thomas; Helgaker, Trygve & Jansik, Branislav [Show all 8 contributors for this article] (2008). Variational and robust density fitting of four-center two-electron integrals in local metrics. Journal of Chemical Physics. ISSN 0021-9606. 129(10). doi: 10.1063/1.2956507.
  • Høst, Stinne; Olsen, Jeppe; Branislav, Jansik; Thøgersen, Lea; Jørgensen, Poul & Helgaker, Trygve (2008). The augmented Roothaan-Hall method for optimizing Hartree-Fock and Kohn-Sham density matrices. Journal of Chemical Physics. ISSN 0021-9606. 129(12).
  • Bast, Radovan; Hesselmann, Andreas; Salek, Pawel; Helgaker, Trygve & Saue, Trond (2008). Static and frequency-dependent dipole-dipole polarizabilities of all closed-shell atoms up to radium: a four-component relativistic density functional theory study. ChemPhysChem. ISSN 1439-4235. 9.
  • Kristensen, Kasper; Jørgensen, Poul; Thorvaldsen, Andreas johan & Helgaker, Trygve (2008). Efficient elimination of response parameters in molecular property calculations for variational and nonvariational energies. Journal of Chemical Physics. ISSN 0021-9606. 129(21). doi: 10.1063/1.3023123.
  • Lutnæs, Ola Berg; Helgaker, Trygve & Jaszunski, M (2008). Density-functional calculations of the nuclear magnetic shielding and indirect nuclear spin-spin coupling constants of three isomers of C20. Molecular Physics. ISSN 0026-8976. 106(20), p. 2357–2365. doi: 10.1080/00268970802467994.
  • Dahle, Pål; Helgaker, T; Jonsson, Dan Johan & Taylor, PR (2008). Second-order Moller-Plesset calculations on the water molecule using Gaussian-type orbital and Gaussian-type geminal theory. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 10(23), p. 3377–3382. doi: 10.1039/b803577f.
  • Dahle, Pål; Helgaker, Trygve; Jonsson, Dan & Taylor, Peter R. (2007). Explicit Electron Correlation by a Combined Use of Gaussian-Type Orbitals and Gaussian-Type Geminals. In Simos, Theodore E. & Maroulis, George (Ed.), COMPUTATION IN MODERN SCIENCE AND ENGINEERING: Proceedings of the International Conference on Computational Methods in Science and Engineering 2007 (ICCMSE 2007): VOLUME 2, PARTS A and B. AIP Publishing (American Institute of Physics). ISSN 978-0-7354-0478-6. p. 187–190.
  • Helgaker, Trygve; Lutnæs, Ola Berg & Jaszunski, Michal (2007). Density-functional and coupled-cluster singles-and-doubles calculations of the nuclear shielding and indirect nuclear spin-spin coupling constants of o-benzyne. Journal of Chemical Theory and Computation. ISSN 1549-9618. 3, p. 86–94. doi: 10.1021/ct600234n.
  • Salek, Pawel; Høst, Stinne; Thøgersen, Lea; Jørgensen, Poul; Manninen, Pekka & Olsen, Jeppe [Show all 12 contributors for this article] (2007). Linear-scaling implementation of molecular electronic self-consistent field theory. Journal of Chemical Physics. ISSN 0021-9606. 126.
  • Jansik, Branislav; Høst, Stinne; Jørgensen, Poul; Olsen, Jeppe & Helgaker, Trygve (2007). Linear-scaling symmetric square-root decomposition of the overlap matrix. Journal of Chemical Physics. ISSN 0021-9606. 126.
  • Tew, David P.; Klopper, Wim & Helgaker, Trygve (2007). Electron correlation: the many-body problem at the heart of chemistry. Journal of Computational Chemistry. ISSN 0192-8651. 28, p. 1307–1320.
  • Coriani, Sonia; Høst, Stinne; Jansik, Branislav; Thøgersen, Lea; Olsen, Jeppe & Jørgensen, Poul [Show all 10 contributors for this article] (2007). Linear-scaling implementation of molecular response theory in self-consistent field electronic-structure theory. Journal of Chemical Physics. ISSN 0021-9606. 126.
  • Reine, Simen Sommerfelt; Tellgren, Erik & Helgaker, Trygve (2007). A unified scheme for the calculation of differentiated and undifferentiated molecular integrals over solid-harmonic Gaussians. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 9, p. 4771–4779. doi: 10.1039/b705594c.
  • Skomorowski, Wojciech; Pecul, Magdalena; Salek, Pawel & Helgaker, Trygve (2007). Electronic circular dichroism of disulphide bridge: Ab initio quantum-chemical calculations. Journal of Chemical Physics. ISSN 0021-9606. 127. doi: 10.1063/1.2759203.
  • Peach, Michael J. G.; Tellgren, Erik; Salek, Pawel; Helgaker, Trygve & Tozer, David J. (2007). Structural and Electronic Properties of Polyacetylene and Polyyne from Hybrid and Coulomb-Attenuated Density Functionals. Journal of Physical Chemistry A. ISSN 1089-5639. 111, p. 11930–11935. doi: 10.1021/jp0754839.
  • Dahle, Pål; Helgaker, T; Jonsson, D & Taylor, PR (2007). Accurate quantum-chemical calculations using Gaussian-type geminal and Gaussian-type orbital basis sets: applications to atoms and diatomics. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 9. doi: 10.1039/b616488a.
  • Coriani, Sonia; Haaland, Arne; Helgaker, Trygve & Jørgensen, Poul (2006). The Equilibrium Structure of Ferrocene. ChemPhysChem. ISSN 1439-4235. 7, p. 245–249. doi: 10.1002/cphc.20050033.
  • Peach, Michael J. G.; Helgaker, Trygve; Salek, Pawel; Keal, Thomas W.; Lutnæs, Ola Berg & Tozer, David J. [Show all 7 contributors for this article] (2006). Assessment of a Coulomb-attenuated exchange-correlation energy functional. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 8, p. 558–562. doi: 10.1039/b511865d.
  • Ferrighi, Lara; Frediani, Luca; Cappelli, Chiara; Salek, Pawel; Ågren, Hans & Helgaker, Trygve [Show all 7 contributors for this article] (2006). Density-functional-theory study of the electric-field-induced second harmonic generation (EFISHG) og push-pull phenylpolyenes in solution. Chemical Physics Letters. ISSN 0009-2614. 425, p. 267–272.
  • Paterson, Martin J.; Christiansen, Ove; Pawlowski, Filip Ludwik; Jørgensen, Poul; Hattig, Christof & Helgaker, Trygve [Show all 7 contributors for this article] (2006). Benchmarking two-photon absorption with CC3 quadratic response theory, and comparison with density-functional response theory. Journal of Chemical Physics. ISSN 0021-9606. 124.
  • Lutnæs, Ola Berg; Teale, Andrew M.; Helgaker, Trygve & Tozer, David J. (2006). Rotational g tensors calculated using hybrid exchange-correlation functionals with the optimized effective potential approach. Journal of Chemical Theory and Computation. ISSN 1549-9618. 2, p. 827–834.
  • Keal, Thomas W.; Helgaker, Trygve; Salek, Pawel & Tozer, David J. (2006). Choice of exchange-correlation functional for computing NMR indirect spin-spin coupling constants. Chemical Physics Letters. ISSN 0009-2614. 425, p. 163–166. doi: 10.1016/j.cplett.2006.05.032.
  • Helgaker, Trygve; Hennum, Alf Christian & Klopper, Wim (2006). A second-quantization framework for the unified treatment of relativistic and nonrelativistic molecular perturbations by response theory. Journal of Chemical Physics. ISSN 0021-9606. 125. doi: 10.1063/1.2198527.
  • Høst, Stinne; Olsen, Jeppe; Jansik, Branislav; Jørgensen, Poul; Reine, Simen & Helgaker, Trygve [Show all 8 contributors for this article] (2006). Towards black-box linear scaling optimization in Hartree-Fock and Kohn-Sham theories. Lecture Series on Computer and Computational Sciences. ISSN 1573-4196. 6, p. 177–189.
  • Wilson, David John; Helgaker, Trygve & Rizzo, Antonio (2006). The magnetizability, rotational g tensor and quadrupole moment of the boron trihalides. Molecular Physics. ISSN 0026-8976. 104.
  • Salek, Pawel; Helgaker, Trygve; Vahtras, Olav; Ågren, Hans; Jonsson, Dan & Gauss, Jurgen (2005). A comparison of density-functional-theory and coupled-cluster frequency-dependent polarizabilities and hyperpolarizabilities. Molecular Physics. ISSN 0026-8976. 103, p. 439–450.
  • Mohn, Chris E.; Wilson, David J.D.; Lutnæs, Ola B.; Helgaker, Trygve & Ruud, Kenneth (2005). The rotational g tensor as a benchmark for ab initio molecular property calculations. Advances in Quantum Chemistry. ISSN 0065-3276. 50.
  • Sellevåg, Stig Rune; Stenstrøm, Yngve; Helgaker, Trygve & Nielsen, Claus (2005). Atmospheric Chemistry of CHF2CHO: Study of the IR and UV-Vis Absorption Cross Sections, Photolysis, and OH-, Cl-, and NO3-Initiated Oxidation. Journal of Physical Chemistry A. ISSN 1089-5639. 109, p. 3652–3662. doi: 10.1021/jp050313m.
  • Wilson, David John; Mohn, Chris Erik & Helgaker, Trygve (2005). The Rotational g Tensor as a Benchmark for Density-Functional Theory Calculations of Molecular Magnetic Properties. Journal of Chemical Theory and Computation. ISSN 1549-9618. 123, p. 877–888. doi: 10.1021/ct050101t.
  • Rizzo, Antonio; Cappelli, Chiara; Junquera-Hernández, José Miguel; Sánchez de Merás, Alfredo M. J.; Sánchez-Marín, José & Wilson, David John [Show all 7 contributors for this article] (2005). A computational study of some electric and magnetic properties of gaseous BF3 and BCl3. Journal of Chemical Physics. ISSN 0021-9606. 123. doi: 10.1063/1.2034487.
  • Coriani, Sonia; Marchesan, Domenico; Gauss, Jurgen; Hattig, Christof; Helgaker, Trygve & Jørgensen, Poul (2005). The accuracy of ab initio molecular geometries for systems containing second-row atoms. Journal of Chemical Physics. ISSN 0021-9606. 123. doi: 10.1063/1.2104387.
  • Rudberg, Elias; Salek, Pawel; Helgaker, Trygve & Ågren, Hans (2005). Calculations of two-photon charge-transfer excitations using Coulomb-attenuated density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 123. doi: 10.1063/1.2104367.
  • Olsen, Jeppe; Jørgensen, Poul; Helgaker, Trygve & Oddershede, Jens (2005). Quadratic Response Functions in a Second-Order Polarization Propagator Framework. Journal of Physical Chemistry A. ISSN 1089-5639. 109, p. 11618–11628. doi: 10.1021/jp054207w.
  • Mohn, Chris Erik; Wilson, David John; Lutnæs, Ola Berg; Helgaker, Trygve & Ruud, Kenneth (2005). The rotational g tensor as a benchmark for ab initio molecular property calculations. Advances in Quantum Chemistry. ISSN 0065-3276. 50, p. 77–90. doi: 10.1016/S0065.
  • Rizzo, A; Cappelli, C; Jansik, B; Jonsson, D; Salek, P & Coriani, S [Show all 9 contributors for this article] (2005). Density-functional theory study of electric and magnetic properties of hexafluorobenzene in the vapor phase. Journal of Chemical Physics. ISSN 0021-9606. 122.
  • Salek, P; Helgaker, Trygve Ulf & Saue, T (2005). Linear response at the 4-component relativistic density-functional level: application to the frequency-dependent dipole polarizability of Hg, AuH and PtH2. Chemical Physics. ISSN 0301-0104. 311.
  • Thogersen, L; Olsen, J; Kohn, A; Jorgensen, P; Salek, P & Helgaker, Trygve Ulf (2005). The trust-region self-consistent field method in Kohn-Sham density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 123.
  • Cybulski, H; Pecul, Magdalena; Pecul, M; Helgaker, Trygve & Jaszunski, M (2005). Theoretical studies of nuclear magnetic resonance parameters for the proton-exchange pathways in porphyrin and porphycene. Journal of Physical Chemistry A. ISSN 1089-5639. 109.
  • Helgaker, Trygve & Pecul, Magdalena (2004). Spin-Spin Coupling Constants with HF and DFT Methods. In Kaupp, Martin; Bühl, Michael & Malkin, Vladimir G. (Ed.), Calculation of NMR and EPR Parameters: Theory and Applications. Wiley-VCH. ISSN 3-527-30779-6. p. 101–121.
  • Helgaker, Trygve; Ruden, Torgeir Andersen; Jørgensen, Poul; Olsen, Jeppe & Klopper, Wim (2004). A priori calculation of molecular properties to chemical accuracy. Journal of Physical Organic Chemistry. ISSN 0894-3230. 17, p. 913–933.
  • Norman, Patrick; Ruud, Kenneth & Helgaker, Trygve (2004). Density-functional theory calculations of optical rotatory dispersion in the nonresonant and resonant frequency regions. Journal of Chemical Physics. ISSN 0021-9606. 120(11), p. 5027–5035.
  • Pecul, Magdalena; Pecul, Magdalena; Ruud, Kenneth; Rizzo, Antonio & Helgaker, Trygve (2004). Conformational effects on the optical rotation of alanine and proline. Journal of Physical Chemistry A. ISSN 1089-5639. 108(19), p. 4269–4276.
  • Pecul, Magdalena; Pecul, Magdalena; Ruud, Kenneth & Helgaker, Trygve (2004). Density functional theory calculation of electronic circular dichroism using London orbitals. Chemical Physics Letters. ISSN 0009-2614. 388, p. 110–119.
  • Lutnæs, Ola Berg; Ruden, Torgeir Andersen & Helgaker, Trygve (2004). The performance of hybrid density functional theory for the calculation of indirect nuclear spin-spin coupling constants in substituted hydrocarbons. Magnetic Resonance in Chemistry. ISSN 0749-1581. 42, p. S117–S127.
  • Ruden, Torgeir Andersen; Helgaker, Trygve & Jaszunski, Michal (2004). The NMR indirect nuclear spin-spin coupling constants for some small rigid hydrocarbons: molecular equilibrium values and vibrational corrections. Chemical Physics. ISSN 0301-0104. 296, p. 53–62.
  • Ratajczyk, Tomasz; Pecul, Magdalena; Sadlej, Joanna & Helgaker, Trygve (2004). Potential energy and spin-spin coupling constants surface of glycolaldehyde. Journal of Physical Chemistry A. ISSN 1089-5639. 108, p. 2758–2769.
  • Watson, Mark A.; Handy, Nicholas C.; Cohen, Aron J. & Helgaker, Trygve (2004). Density-functional generalized-gradient and hybrid calculations of electromagnetic properties using Slater basis sets. Journal of Chemical Physics. ISSN 0021-9606. 120, p. 7252–7261.
  • Soncini, Alessandro; Lazzeretti, Paolo; Bakken, Vebjørn & Helgaker, Trygve (2004). Calculation of electric dipole hypershieldings at the nuclei in the Hellmann-Feynman approximation. Journal of Chemical Physics. ISSN 0021-9606. 120, p. 3142–3151.
  • Thøgersen, Lea; Olsen, Jeppe; Yeager, Danny; Jørgensen, Poul; Salek, Pawel Krzysztof & Helgaker, Trygve (2004). The trust-region self-consistent field method: Towards a black-box optimization in Hartree-Fock and Kohn-Sham theories. Journal of Chemical Physics. ISSN 0021-9606. 121, p. 16–27.
  • Keal, Thomas W.; Tozer, David J. & Helgaker, Trygve (2004). GIAO shielding constants and indirect spin-spin couping constants: performance of density functional methods. Chemical Physics Letters. ISSN 0009-2614. 391, p. 374–379.
  • Watson, Mark A.; Salek, Pawel Krzysztof; Macak, Peter & Helgaker, Trygve (2004). Linear-scaling formation of Kohn-Sham Hamiltonian: Application to the calculation of excitation energies and polarizabilities of large molecular systems. Journal of Chemical Physics. ISSN 0021-9606. 121, p. 2915–2931.
  • Jensen, Frank & Helgaker, Trygve (2004). Polarization consistent basis sets. V. The elements Si-Cl. Journal of Chemical Physics. ISSN 0021-9606. 121, p. 3463–3470.
  • Bakken, Vebjørn & Helgaker, Trygve (2004). The expansion of hydrogen states in Gaussian orbitals. Theoretical Chemistry Accounts. ISSN 1432-881X. 112, p. 124–134.
  • Watson, Mark A.; Salek, Pawel Krzysztof; Macak, Peter; Jaszunski, Michal & Helgaker, Trygve (2004). The calculation of indirect nuclear spin-spin coupling constants in large molecules. Chemistry - A European Journal. ISSN 0947-6539. 10, p. 4627–4639.
  • Ruden, Torgeir Andersen; Helgaker, Trygve; Jørgensen, Poul & Olsen, Jeppe (2004). Coupled-cluster connected quadruples and quintuples corrections to the harmonic vibrational frequencies and equilibrium bond distances of HF, N-2, F-2, and CO. Journal of Chemical Physics. ISSN 0021-9606. 121, p. 5874–5884.
  • Coriani, Sonia; Helgaker, Trygve; Jørgensen, Poul & Klopper, Wim (2004). A closed-shell coupled-cluster treatment of the Breit-Pauli first-order relativistic energy correction. Journal of Chemical Physics. ISSN 0021-9606. 121, p. 6591–6598.
  • Klopper, Wim; Coriani, Sonia; Helgaker, Trygve & Jørgensen, Poul (2004). First-order relativistic corrections to response properties: the hyperpolarizability of the Ne atom. Journal of Physics B: Atomic, Molecular and Optical Physics. ISSN 0953-4075. 37, p. 3753–3763.
  • Bruun, Jesper; Helgaker, Trygve & Jensen, Frank (2004). A comparison of polarization and bond functions for density functional calculations. Molecular Physics. ISSN 0026-8976. 102, p. 2559–2562.
  • Bakken, Vebjørn; Helgaker, Trygve & Uggerud, Einar (2004). Models of fragmentations induced by electron attachment to protonated peptides. European Journal of Mass Spectrometry. ISSN 1469-0667. 102, p. 625–638.
  • Helgaker, Trygve Ulf; Jørgensen, Poul; Olsen, Jeppe & Klopper, Willem Maarten (2003). Wave-Function Based Quantum Chemistry. In Bultinck, Patrick; Tollenaere, Jan P.; Winter, Hans De & Langenaeker, Wilfried (Ed.), Computational Medicinal Chemistry and Drug Discovery. Marcel Dekker. ISSN 0-8247-4774-7. p. 57–88.
  • Ruden, Torgeir Andersen; Lutnæs, Ola Berg & Helgaker, Trygve Ulf (2003). Vibrational corrections to indirect nuclear spin--spin coupling constants calculated by density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 118(21), p. 9572–9581.
  • Pawlowski, Filip; Halkier, Asger; Jørgensen, Poul; Bak, Keld L.; Helgaker, Trygve Ulf & Klopper, Willem Maarten (2003). Accuracy of spectroscopic constants of diatomic molecules from ab initio calculations. Journal of Chemical Physics. ISSN 0021-9606. 118, p. 2539–2549.
  • Hald, Kasper; Jørgensen, Poul; Coriani, Sonia; Hattig, Christof & Helgaker, Trygve Ulf (2003). A Lagrangian, integral-density direct formulation and implementation of the analytic CCSD and CCSD(T) gradients. Journal of Chemical Physics. ISSN 0021-9606. 118, p. 2985–2998.
  • Pecul, Magdalena & Helgaker, Trygve Ulf (2003). The spin-spin coupling constants in ethane, methanol and methylamine: a comparison of DFT, MCSCF, and CCSD results. International Journal of Molecular Sciences. ISSN 1661-6596. 4, p. 143–157.
  • Ruden, Torgeir Andersen; Helgaker, Trygve Ulf; Jørgensen, Poul & Olsen, Jeppe (2003). Coupled-cluster connected-quadruples corrections to atomization energies. Chemical Physics Letters. ISSN 0009-2614. 371, p. 62–67.
  • Rizzo, Antonio; Ruud, Kenneth; Helgaker, Trygve Ulf; Salek, Pawel; Ågren, Hans & Vahtras, Olav (2003). Sternheimer shieldings and EFG polarizabilities: a density-functional theory study. Chemical Physics Letters. ISSN 0009-2614. 372, p. 377–385.
  • Pecul, Magdalena; Sadlej, Joanna & Helgaker, Trygve Ulf (2003). Calculations of hydrogen-bond-transmitted indirect nuclear spin-spin couplings: comparison of density-functional and ab initio methods. Chemical Physics Letters. ISSN 0009-2614. 372, p. 476–484.
  • Jaszunski, Michal; Ruud, Kenneth & Helgaker, Trygve Ulf (2003). DFT calculation of the NMR indirect spin-spin coupling constants of C60. Molecular Physics. ISSN 0026-8976. 101, p. 1997–2002.
  • Ruden, Torgeir Andersen; Taylor, Paul & Helgaker, Trygve Ulf (2003). Automated calculation of fundamental frequencies: application to AlH3 using the CCSD(T) method. Journal of Chemical Physics. ISSN 0021-9606. 119, p. 1951–1960.
  • Salek, Pawel; Vahtras, Olav; Guo, Jingheng; Luo, Yi; Helgaker, Trygve Ulf & Ågren, Hans (2003). Calculations of two-photon absorption cross sections by means of density-functional theory. Chemical Physics Letters. ISSN 0009-2614. 374, p. 446–452.
  • Cybulski, Hubert; Pecul, Magdalena; Sadlej, Joanna & Helgaker, Trygve Ulf (2003). Characterization of dihydrogen-bonded D-H...H-A complexes on the basis of infrared and magnetic resonance spectroscopic parameters. Journal of Chemical Physics. ISSN 0021-9606. 119, p. 5094–5104.
  • Tunell, Ingvar; Rinkevicius, Zilvinas; Vahtras, Olav; Salek, Pawel; Helgaker, Trygve Ulf & Ågren, Hans (2003). Density-functional theory of non-linear triplet response properties with applications to phosphorescence. Journal of Chemical Physics. ISSN 0021-9606. 119, p. 11024–11034.
  • Jaszunski, Michal; Ruud, Kenneth & Helgaker, Trygve (2003). DFT calculations of the NMR indirect nuclear spin-spin coupling constants in C60. Molecular Physics. ISSN 0026-8976. 101.
  • Rizzo, Antonio; Ruud, Kenneth; Helgaker, Trygve; Salek, Pawel; Ågren, Hans & Vahtras, Olav (2003). Sternheimer shieldings and EFG polarizabilities: a density-functional theory study. Chemical Physics Letters. ISSN 0009-2614. 372.
  • Ruden, Torgeir A.; Lutnæs, Ola B.; Helgaker, Trygve & Ruud, Kenneth (2003). Vibrational corrections to indirect nuclear spin-spin coupling constants calculated by density-functional theory. Journal of Chemical Physics. ISSN 0021-9606. 118.

View all works in Cristin

  • Helgaker, Trygve (2021). Molecular Dynamics and Rovibrational Spectra in a Strong Magnetic Field.
  • Helgaker, Trygve (2021). The Exotic Chemistry in a Strong Magnetic Field.
  • Tellgren, Erik & Helgaker, Trygve (2020). Strong Magnetic Field-Induced Chemical Bonding.
  • Helgaker, Trygve (2020). Hylleraas Centre for Quantum Molecular Sciences – Applying For and Setting Up a Centre of Excellence .
  • Helgaker, Trygve (2020). SFF V: Assessment Criteria — Applying For and Setting Up a Centre of Excellence.
  • Helgaker, Trygve (2020). Quantum Chemistry – A Matter of Life and Death.
  • Helgaker, Trygve (2020). Chemistry in a Strong Magnetic Field.
  • Eriksen, Janus J.; Stopkowicz, Stella; Jagau, Thomas-C. & Helgaker, Trygve (2020). Foreword: Prof. Gauss Festschrift. Molecular Physics. ISSN 0026-8976. 118. doi: 10.1080/00268976.2020.1817247.
  • Helgaker, Trygve (2019). Molecular Magnetic Properties.
  • Helgaker, Trygve (2019). Molecules in magnetic fields.
  • Helgaker, Trygve (2019). Time-independent molecular properties.
  • Helgaker, Trygve (2019). Geometry optimization.
  • Helgaker, Trygve (2019). Hylleraas Centre for Quantum Molecular Sciences.
  • Helgaker, Trygve (2019). Kvantekjemi — på liv og død.
  • Helgaker, Trygve (2019). Hylleraas Centre for Quantum Molecular Sciences: Applying for and Setting up a Centre of Excellence.
  • Helgaker, Trygve (2019). Centre for Data Science and Computational Science.
  • Helgaker, Trygve (2019). Utenomjordisk kjemi.
  • Helgaker, Trygve (2019). Egil A. Hylleraas – en norsk pioner innen kvantemekanikk.
  • Helgaker, Trygve (2019). Utenomjordisk kjemi.
  • Helgaker, Trygve (2019). Kvantemekanikk og kjemi.
  • Helgaker, Trygve (2019). Kvantemekanikk og kjemi.
  • Helgaker, Trygve (2019). Kvantemekanikk og kjemi.
  • Helgaker, Trygve (2019). Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
  • Helgaker, Trygve (2019). Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
  • Helgaker, Trygve (2019). Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
  • Helgaker, Trygve (2019). Chemistry in a Strong Magnetic Field.
  • Helgaker, Trygve (2019). Egil A. Hylleraas - a pioneer of computational quantum mechanics.
  • Helgaker, Trygve (2019). Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
  • Helgaker, Trygve (2019). Quantum-Chemical Calculations of NMR Parameters.
  • Helgaker, Trygve (2019). Chemistry in a strong magnetic field.
  • Helgaker, Trygve & Isaksen, Karoline Kvellestad (2019). Kan sjaman Durek Verrett snu atomer? – Vi snur atomkjernene hver dag i vitenskap og medisin, svarer forsker. [Newspaper]. forskning.no.
  • Helgaker, Trygve; Ruud, Kenneth & Røsjø, Bjarne (2019). Forskerne ved Hylleraas-senteret jakter på kjemiens hellige gral. [Newspaper]. Titan.uio.no.
  • Helgaker, Trygve; Svelle, Stian & Haugnes, Gunhild Merete (2019). Datakraft gir forskerne bedre intuisjon og flere ideer. [Newspaper]. Titan.uio.no.
  • Holzer, Christof; Teale, Andrew Michael; Hampe, Florian; Stopkowicz, Stella; Helgaker, Trygve & Klopper, Wim (2019). Erratum: GW quasiparticle energies of atoms in strong magnetic fields (Journal of Chemical Physics (2019) 150 (214112) DOI: 10.1063/1.5093396). Journal of Chemical Physics. ISSN 0021-9606. 151(6). doi: 10.1063/1.5120100.
  • Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2019). Guaranteed convergence of a regularized Kohn-Sham iteration in finite dimensions.
  • Tellgren, Erik; Helgaker, Trygve & Sen, Sangita (2019). Unifying kinetic energy density and current density in density-functional theory.
  • Tellgren, Erik; Helgaker, Trygve & Sen, Sangita (2019). Unifying kinetic energy density and current density in density-functional theory.
  • Tellgren, Erik; Helgaker, Trygve & Sen, Sangita (2019). Unifying kinetic energy density and current density in density-functional theory.
  • Helgaker, Trygve; Borgoo, Alex; Dimitrova, Maria; Gauss, Jurgen; Hampe, Florian & Holzer, Christof [Show all 13 contributors for this article] (2018). Diamagnetism and Paramagnetism in Atoms and Molecules.
  • Helgaker, Trygve (2018). Hylleraas Centre for Quantum Molecular Sciences.
  • Helgaker, Trygve (2018). Closed-Shell Molecular Paramagnetism.
  • Helgaker, Trygve (2018). Hylleraas Centre for Quantum Molecular Sciences — Ny giv i nytt senter, kvinnelige rollemodeller og nytt initiativ til karrierestøtte, .
  • Helgaker, Trygve (2018). Utenomjordisk kjemi.
  • Helgaker, Trygve (2018). Molecular Derivatives and Properties.
  • Helgaker, Trygve; Borgoo, Alex; Gauss, Jurgen; Hampe, Florian; Klopper, Wim & Reimann, Sarah [Show all 9 contributors for this article] (2018). Closed-Shell Molecular Paramagnetism.
  • Helgaker, Trygve; Borgoo, Alex; Gauss, Jurgen; Hampe, Florian; Klopper, Wim & Reimann, Sarah [Show all 9 contributors for this article] (2018). Closed-Shell Molecular Paramagnetism.
  • Helgaker, Trygve (2018). Four-Way Correspondence of Density-Functional Theory.
  • Helgaker, Trygve; Borgoo, Alex; Gauss, Jurgen; Hampe, Florian; Klopper, Wim & Stopkowicz, Stella [Show all 8 contributors for this article] (2018). Closed-Shell Molecular Magnetism.
  • Helgaker, Trygve (2018). Chemistry in Strong Magnetic Fields.
  • Helgaker, Trygve (2018). Kvantemekanikk og kjemi.
  • Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve (2018). Generalized Kohn-Sham iteration on Banach Spaces.
  • Tellgren, Erik; Lange, Kai Kaarvann; Sagvolden, Espen; Kvaal, Simen; Austad, Jon & Reimann, Sarah [Show all 9 contributors for this article] (2018). Quantum chemistry for strong magnetic fields.
  • Helgaker, Trygve & Ruud, Kenneth (2018). Langsiktig fra Forskningsrådet. Khrono.no. ISSN 1894-8995.
  • Helgaker, Trygve & Ruud, Kenneth (2017). 10 år med god kjemi. Nordlys. ISSN 0805-5440.
  • Helgaker, Trygve (2017). Four-Way Correspondence of Density-Functional Theory.
  • Helgaker, Trygve (2017). Hylleraas Centre.
  • Helgaker, Trygve (2017). CTCC Review.
  • Helgaker, Trygve (2017). Molecular Magnetic Properties.
  • Helgaker, Trygve (2017). Molecules in Magnetic Fields.
  • Helgaker, Trygve (2017). Time-Dependent Molecular Properties.
  • Helgaker, Trygve (2017). Geometry Optimization.
  • Helgaker, Trygve (2017). Quantum Chemistry in Magnetic Fields.
  • Helgaker, Trygve (2017). Four-Way Correspondence of Density-Functional Theory.
  • Helgaker, Trygve (2017). Density-Functional Theory in Magnetic Fields.
  • Helgaker, Trygve (2017). The Role of the Hohenberg-Kohn Theorem in Density-Functional Theory.
  • Helgaker, Trygve (2017). Density-Functional Theory in Magnetic Fields.
  • Helgaker, Trygve (2017). Hylleraas Centre for Quantum Molecular Sciences.
  • Helgaker, Trygve (2017). The Role of the Hohenberg-Kohn Theorem in Density-Functional Theory.
  • Helgaker, Trygve (2017). Principles of Density-Functional Theory.
  • Pal, Sourav; Helgaker, Trygve & Savin, Andreas (2017). Foreword to special issue in honour of Debashis Mukherjee. Molecular Physics. ISSN 0026-8976. 115(21-22), p. 2627–2628. doi: 10.1080/00268976.2017.1380450.
  • Lüthi, Hans P. & Helgaker, Trygve (2017). A tribute to Jan Erik Almlof. Molecular Physics. ISSN 0026-8976. 115(17-18), p. 2033–2042. doi: 10.1080/00268976.2017.1293305.
  • Helgaker, Trygve (2016). Derivatives and Properties.
  • Borgoo, Alex; Tozer, David J.; Teale, Andrew Michael & Helgaker, Trygve (2016). Approximate orbital-free non-interacting kinetic energy density functionals from density scaling.
  • Wirz, Lukas Nico; Reine, Simen Sommerfelt; Pedersen, Thomas Bondo & Helgaker, Trygve (2016). Efficient auxiliary bases for the non-robust pair atomic resolution of the identity (PARI) method.
  • Rebolini, Elisa; Izsak, Robert; Reine, Simen Sommerfelt; Helgaker, Trygve & Pedersen, Thomas Bondo (2016). Comparison of three efficient approximate exact-exchange algorithms: chain-of-spheres, pair-atomic resolution of the identity, and the auxiliary density matrix method.
  • Helgaker, Trygve (2016). Molecules in Magnetic Fields.
  • Helgaker, Trygve (2016). Recent Developments in Current-Density-Functional Theory.
  • Helgaker, Trygve (2016). The Role of the Hohenberg–Kohn Theorem in Density-Functional Theory.
  • Helgaker, Trygve (2016). The Role of the Hohenberg–Kohn Theorem in Density-Functional Theory.
  • Helgaker, Trygve & Lüthi, Hans Peter (2016). Jan Almlöf.
  • Helgaker, Trygve (2016). Current-Density-Functional Theory of Molecules in Weak and Strong Magnetic Fields.
  • Helgaker, Trygve (2016). Current-Density-Functional Theory of Molecules in Weak and Strong Magnetic Fields.
  • Gori-Giorgi, Paola; Helgaker, Trygve; Scuseria, Gustavo E.; Silvi, Bernard & Toulouse, Julien (2016). Foreword for special issue of Molecular Physics in honour of Andreas Savin. Molecular Physics. ISSN 0026-8976. 114, p. 909–909. doi: 10.1080/00268976.2016.1160647.
  • Helgaker, Trygve; Knowles, Peter J.; Lee, Timothy J.; RIce, Julia E. & Tozer, David J. (2015). Foreword. Molecular Physics. ISSN 0026-8976. 113, p. 1509–1510. doi: 10.1080/00268976.2015.1047162.
  • Borgoo, Alex; Helgaker, Trygve & Tozer, David J. (2015). Exploring homogeneity under density scaling and Molecular binding in post-Kohn–Sham orbital-free DFT .
  • Borgoo, Alex; Teale, Andrew Michael & Helgaker, Trygve (2015). Excitation energies from ensemble DFT.
  • Borgoo, Alex; Teale, Andrew Michael & Helgaker, Trygve (2015). Excitation energies from ensemble DFT.
  • Helgaker, Trygve (2015). Molecular magnetic properties.
  • Helgaker, Trygve (2015). Time-Independent molecular properties.
  • Helgaker, Trygve (2015). Geometry optimisation.
  • Helgaker, Trygve (2015). Density-functional theory in magnetic fields.
  • Helgaker, Trygve (2015). Fundamentals of density-functional theory.
  • Helgaker, Trygve (2015). Density-functional theory in magnetic fields.
  • Helgaker, Trygve (2015). Egil A. Hylleraas.
  • Mennucci, Benedetta; Eisenstein, Odile; Fliegl, Heike; Hopmann, Kathrin Helen; Helgaker, Trygve & Ruud, Kenneth (2015). FemEx—Female Excellence in Theoretical and Computational Chemistry. International Journal of Quantum Chemistry. ISSN 0020-7608. doi: 10.1002/qua.24961.
  • Helgaker, Trygve (2015). Density-functional theory in magnetic fields.
  • Helgaker, Trygve (2015). Egil A. Hylleraas.
  • Helgaker, Trygve (2015). Moreau–Yosida Regularised DFT.
  • Helgaker, Trygve (2015). Magnetisk binding.
  • Helgaker, Trygve (2015). Density-Functional Theory in Magnetic Fields .
  • Helgaker, Trygve (2015). Exact but Differentiable Formulation of Density-Functional Theory.
  • Helgaker, Trygve (2015). Exact but Differentiable Formulation of Density-Functional Theory.
  • Helgaker, Trygve & Reine, Simen Sommerfelt (2015). Fremtidens nanomedisiner bygger på kvantekjemi. [Journal]. Apollon.
  • Tellgren, Erik; Teale, Andrew Michael; Ekström, Ulf Egil; Kvaal, Simen; Sagvolden, Espen & Helgaker, Trygve (2015). Current density functional theory for molecular systems in strong magnetic fields.
  • Sagvolden, Espen; Tellgren, Erik; Ekström, Ulf Egil & Helgaker, Trygve (2014). Cusp based DFT functionals.
  • Reine, Simen Sommerfelt; Helgaker, Trygve; Merlot, Patrick; Kjærgaard, Thomas; Borgoo, Alex & Izsak, Robert (2014). Charge-constrained auxiliary-density-matrix methods for the Hartree-Fock exchange contribution.
  • Helgaker, Trygve (2014). Molecular Magnetic Properties.
  • Helgaker, Trygve (2014). The Molecular Hamiltonian.
  • Helgaker, Trygve (2014). Time-Independent Molecular Properties.
  • Helgaker, Trygve (2014). Basis Sets for Electron Correlation.
  • Helgaker, Trygve (2014). Basis Functions and Basis Sets.
  • Helgaker, Trygve (2014). Moelcular Integral Evaluation.
  • Helgaker, Trygve (2014). Density-Functional Theory.
  • Teale, Andrew Michael; Furness, James; Tellgren, Erik; Ekström, Ulf Egil & Helgaker, Trygve (2014). Density Functional Theory for Molecules in Magnetic Fields.
  • Helgaker, Trygve; Borgoo, Alex; Ekström, Ulf Egil; Furness, James; Hoffmann, Mark & Kvaal, Simen [Show all 12 contributors for this article] (2014). Density-Functional Theory in Magnetic Fields.
  • Helgaker, Trygve; Hoffmann, Mark; Lange, Kai Kaarvann; Soncini, Alessandro & Tellgren, Erik (2014). Molecules in Strong Magnetic Fields.
  • Helgaker, Trygve; Kvaal, Simen; Ekström, Ulf Egil & Teale, Andy (2014). Differentiable but Exact Formulation of Density-Functional Theory.
  • Helgaker, Trygve (2014). Beregningskjemi.
  • Helgaker, Trygve (2014). Quantum-Chemical Calculations of NMR Parameters.
  • Helgaker, Trygve; Kvaal, Simen; Ekström, Ulf Egil & Teale, Andrew Michael (2014). Differentiable but Exact Formulation of Density-Functional Theory.
  • Helgaker, Trygve; Kvaal, Simen; Teale, Andrew Michael; Ekström, Ulf Egil; Jørgensen, Poul & Olsen, Jeppe (2014). Differentiable but Exact Formulation of Density-Functional Theory.
  • Helgaker, Trygve; Kvaal, Simen; Teale, Andrew Michael & Ekström, Ulf Egil (2014). Differentiable but Exact Formulation of Density-Functional Theory.
  • Helgaker, Trygve (2014). Nobelprisen i kjemi 2013 og noe annet...
  • Borgoo, Alex; Teale, Andrew Michael & Helgaker, Trygve (2014). Ensemble energies: An alternative route to excitation energies.
  • Pedersen, Thomas Bondo; Rekkedal, Johannes Andreas; Leikanger, Karl R.; Iozzi, Maria Francesca; Coriani, Sonia & Teale, Andrew Michael (2014). Molecular Properties in the Random Phase Approximation.
  • Stopkowicz, Stella & Helgaker, Trygve (2014). Coupled-Cluster Theory for Molecules in Strong Magnetic Fields.
  • Sagvolden, Espen; Tellgren, Erik; Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2013). Building blocks of Current Density Functional Theory.
  • Sagvolden, Espen; Tellgren, Erik; Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve (2013). Building blocks of Current Density Functional Theory.
  • Ekström, Ulf Egil; Kvaal, Simen; Borgoo, Alex; Helgaker, Trygve; Sagvolden, Espen & Tellgren, Erik (2013). Moreau-Yosida regularization of DFT.
  • Kvaal, Simen; Ekström, Ulf Egil; Tellgren, Erik; Borgoo, Alex; Helgaker, Trygve & Sagvolden, Espen (2013). Moreau-Yosida regularization of DFT.
  • Borgoo, Alex; Sagvolden, Espen; Teale, Andrew Michael; Knecht, Stefan; Savin, A & Helgaker, Trygve (2013). Adiabatic connection for ensemble energies: \\An alternative route to excitation energies.
  • Borgoo, Alex; Savin, A; Knecht, Stefan; Teale, Andrew Michael; Helgaker, Trygve & Sagvolden, Espen (2013). Adiabatic connection for ensemble energies: \\An alternative route to excitation energies.
  • Stopkowicz, Stella & Helgaker, Trygve (2013). Correlated molecular energies in strong magnetic fields.
  • Pedersen, Thomas Bondo; Rekkedal, Johannes Andreas; Iozzi, Maria Francesca; Coriani, Sonia; Teale, Andrew Michael & Helgaker, Trygve (2013). Molecular Properties in the Random Phase Approximation.
  • Helgaker, Trygve (2013). Molecular magnetism and density-functional theory in magnetic fields.
  • Helgaker, Trygve (2013). Molecular Magnetic Properties.
  • Helgaker, Trygve (2013). Molecules in Strong Magnetic Fields.
  • Helgaker, Trygve (2013). Metoder i teoretisk og beregningsorientert kjemi / Kvantekjemiske beregninger i moderne kjemisk forskning,
  • Helgaker, Trygve (2013). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2013). Nobel Prize 2013.
  • Helgaker, Trygve (2013). Molecular magnetic properties.
  • Helgaker, Trygve (2013). TIme-independet molecular properties.
  • Helgaker, Trygve (2013). Geometry optimization.
  • Helgaker, Trygve (2013). Molecular magnetism and density-functional theory in magnetic fields.
  • Helgaker, Trygve (2013). Molecular Magnetism and Density-Functional Theory in Magnetic Fields.
  • Helgaker, Trygve (2013). Molecules in Strong Magnetic Fields.
  • Helgaker, Trygve (2013). Molecular magnetism and density-functional theory in magnetic fields.
  • Helgaker, Trygve (2013). Density-functional theory, with and without a magnetic field.
  • Gauss, Jurgen; Helgaker, Trygve & Stanton, John F. (2012). Foreword. Molecular Physics. ISSN 0026-8976. 110, p. 2313–2313. doi: 10.1080/00268976.2012.731766.
  • Helgaker, Trygve (2012). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2012). Current-density-functional theory: basic variables and convex conjugation.
  • Helgaker, Trygve (2012). Magnetic resonance parameteres.
  • Helgaker, Trygve (2012). Molecules in an external magnetic field.
  • Helgaker, Trygve (2012). The electronic Hamiltonian.
  • Helgaker, Trygve (2012). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2012). Time-independent molecular properties.
  • Helgaker, Trygve (2012). Geometry optimization.
  • Helgaker, Trygve (2012). Basis sets for electron correlation.
  • Helgaker, Trygve (2012). Basis functions and basis sets.
  • Helgaker, Trygve (2012). High-accuracy quantum chemistry.
  • Helgaker, Trygve (2012). Chemical bonding in strong magnetic fields.
  • Helgaker, Trygve (2012). Molecular magnetic propeties.
  • Helgaker, Trygve (2012). The molecular Hamiltonian.
  • Helgaker, Trygve (2012). Time-independent molecular properties.
  • Helgaker, Trygve (2012). Molecular integral evaluation.
  • Helgaker, Trygve (2012). Basis sets for electron correlation.
  • Helgaker, Trygve (2012). Basis functions and basis sets.
  • Helgaker, Trygve (2012). Density-functional theory.
  • Helgaker, Trygve (2012). Chemical bonding in strong magnetic fields.
  • Helgaker, Trygve (2012). Molecular bonding in strong magnetic fields.
  • Helgaker, Trygve (2012). Density-functional theory in magnetic fields.
  • Helgaker, Trygve (2012). Kvantekmekanikk på datamaskiner: kjemiens nye verktøy.
  • Helgaker, Trygve (2012). Density-functional theory in magnetic fields.
  • Helgaker, Trygve (2011). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2011). Molecular Electronic-Structure Theory: Yesterday, Today and Tomorrow.
  • Helgaker, Trygve (2011). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2011). Quantum chemistry: wave-function and density-functional methods.
  • Helgaker, Trygve (2011). Importing ab-initio theory into DFT. some applications of the Lieb variation principle.
  • Helgaker, Trygve (2011). Kvantemekanikk på datamaskiner: kjemiens nye verktøy.
  • Helgaker, Trygve (2011). Centre for Theoretical and Computational Chemistry.
  • Helgaker, Trygve (2011). Kvantemekanikk på datamaskiner: kjemiens nye verktøy.
  • Helgaker, Trygve (2011). Kvantemekanikk på datamaskiner: kjemiens nye verktøy.
  • Helgaker, Trygve (2011). Molecular bonding in strong magnetic fields.
  • Helgaker, Trygve (2011). Molecular electronic structure in strong magnetic fields.
  • Helgaker, Trygve (2011). Molecules in strong magnetic fields: electron correlation.
  • Helgaker, Trygve (2011). Geometry Optimization.
  • Helgaker, Trygve (2011). TIme-independent molecular properties.
  • Helgaker, Trygve (2011). Molecular Magnetic Properties.
  • Helgaker, Trygve (2011). Molecules in strong magnetic fields: electron correlation.
  • Helgaker, Trygve (2011). Molecular electronic-structure theory; some current trends.
  • Helgaker, Trygve (2011). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2011). Molecules in strong magnetic fields.
  • Helgaker, Trygve; Kaarvann, Lange Kai & Tellgren, Erik (2011). Molecules in strong magnetic fields. META. ISSN 1890-1956. p. 16–18.
  • Helgaker, Trygve (2010). Molecular Magnetic Properties.
  • Helgaker, Trygve (2010). The Molecular Hamiltonian.
  • Helgaker, Trygve (2010). Time-Independent Molecular Properties.
  • Helgaker, Trygve (2010). Basis Sets for Electron Correlation.
  • Helgaker, Trygve (2010). Basis Functions and Basis Sets.
  • Helgaker, Trygve (2010). Molecular Integral Evaluation.
  • Helgaker, Trygve (2010). Density-functional theory.
  • Helgaker, Trygve (2010). The exhaustion of the Schrodinger equation: The accurate calculation of molecular properties of light systems.
  • Helgaker, Trygve (2010). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2010). Geometry optimization.
  • Helgaker, Trygve (2010). Computational Chemistry.
  • Helgaker, Trygve (2010). The calculation of the universal density functional by Lieb maximization.
  • Helgaker, Trygve (2010). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2010). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2010). Ab initio studies for the adiabatic connection in density-functional theory.
  • Helgaker, Trygve (2010). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2010). Convergence properties of the coupled-cluster method: the accurate calculation of molecular properties for light systems.
  • Helgaker, Trygve (2010). The rigorous calculation of the universal density functional by the Lieb variation principle.
  • Helgaker, Trygve (2010). Rigorous calculation of the universal density functional by the Lieb variation principle.
  • Helgaker, Trygve (2010). Ab-initio studies of the adiabatic connection in density-functional teory.
  • Helgaker, Trygve (2010). Calculation and Modeling of Adiabatic-Connection Curves.
  • Helgaker, Trygve (2009). From ab initio methods to density-functional theory.
  • Helgaker, Trygve (2009). Geometry Optimization.
  • Helgaker, Trygve (2009). Molecular Magnetic Properties.
  • Helgaker, Trygve (2009). Time-Independent Molecular Properties.
  • Helgaker, Trygve (2009). The Adiabatic Connection.
  • Helgaker, Trygve (2009). Linear-Scaling Methods for Molecular Energies and Properties.
  • Helgaker, Trygve (2009). The Generalized Adiabatic Connection.
  • Helgaker, Trygve (2009). Computational Chemistry.
  • Helgaker, Trygve (2008). Molecules in strong magnetic fields.
  • Helgaker, Trygve (2008). Organic Quantum Chemistry.
  • Helgaker, Trygve (2008). Molecules in Strong Magnetic Fields.
  • Helgaker, Trygve (2008). New Techniques of Self-Consistent Field Theory.
  • Helgaker, Trygve (2008). The Dalton Quantum-Chemistry Program: Current Capabilities and Ongoing Developments.
  • Helgaker, Trygve (2008). Atomic Orbitals (1 hour), Explicit Correlation (1 hour), Basis sets (1 hour), Molecular Integrals (2 hours), DFT (4 hours), Molecular Hamiltonian (2 hours), Magnetic Properties (2 hours), Time-Independent Properties (2 hours), Benchmarking (1 hour).
  • Helgaker, Trygve (2008). Methods for the calculation of internal and external perturbations of molecular systems.
  • Helgaker, Trygve (2008). The development of methods for the calculation of the response of molecular systems to internal and external perturbations.
  • Helgaker, Trygve (2008). Density-functional theory in quantum chemistry.
  • Helgaker, Trygve (2008). Excitation energies from density-functional theory: some failures and successes.
  • Helgaker, Trygve (2008). The accurate calculation of molecular energies and properties: A tour of high-accuracy quantum-chemical methods.
  • Helgaker, Trygve (2008). The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
  • Helgaker, Trygve (2008). The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
  • Helgaker, Trygve (2008). The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
  • Helgaker, Trygve (2008). The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
  • Helgaker, Trygve (2008). The accurate calculation of molecular energies and properties: a tour of high-accuracy quantum-chemical mthods.
  • Helgaker, Trygve (2008). The Exhaustion of the Schrodinger equation: The accurate calculation of Molecular Properties of Light Systems.
  • Helgaker, Trygve (2008). Centre for Theoretical and Computational Chemistry.
  • Helgaker, Trygve (2007). New techniques of self-consistent field theory.
  • Helgaker, Trygve (2007). Quantative Quantum Chemistry.
  • Helgaker, Trygve (2007). Quantum chemistry - a quantitative tool in chemistry.
  • Helgaker, Trygve (2007). New techniques of self-consistent field theory.
  • Helgaker, Trygve (2007). Strategies for large-scale molecular self-consistent field calculations.
  • Helgaker, Trygve (2007). Explicit electron correlation by a combined use of Gaussian-type orbitals and Gaussian-type geminals.
  • Helgaker, Trygve (2007). Accurate Calculations and Calibration.
  • Helgaker, Trygve (2007). Molecular Magnetic Properties.
  • Helgaker, Trygve (2007). Time-Independent Molecular Properites.
  • Helgaker, Trygve (2007). Geomtry Optimization.
  • Helgaker, Trygve (2007). Expilcit correlation by a combined use of Gaussian-type orbitals and Gaussian-type geminals.
  • Helgaker, Trygve (2007). The calculation of energies and properties of large systems.
  • Helgaker, Trygve (2007). Highly accurate quantum-chemical calculations.
  • Helgaker, Trygve; Helgaker, Trygve; Dahle, Pål; Jonsson, Dan & Taylor, Peter R. (2007). Quantum-chemical calculations with Gaussian-type orbital and geminal basis sets.
  • Helgaker, Trygve (2007). The Calculation of Mocular Properties of Large Systems.
  • Helgaker, Trygve (2007). Relativistic Corrections in Highly Accurate Calculations on Small Molecular Systems.
  • Helgaker, Trygve (2007). The Right Answer for the Right Reason: A Tour of High-Accuracy Quantum-Chemical Calculations.
  • Helgaker, Trygve; Helgaker, Trygve; Dahle, Pål; Jonsson, Dan & Taylor, Peter R. (2007). Quantum-Chemical Calculations Using Gaussian-Type Orbital and Gaussian-Type Geminal Basis Sets.
  • Helgaker, Trygve (2007). Det virtuelle kjemilaboratoriet.
  • Helgaker, Trygve (2007). Centre for Theoretical and Computational Chemistry.
  • Helgaker, Trygve (2007). Kvantekjemi - kjemiens nye verktøy.
  • Helgaker, Trygve (2006). SCF methods for energies and properties of large molecular systems.
  • Helgaker, Trygve (2006). Self-consistent field methods for large molecular systems.
  • Helgaker, Trygve (2006). Methods for Hartree-Fock and Kohn-Sham calculations on large molecular systems.
  • Helgaker, Trygve (2006). Evaluation of Fock/Kohn-Sham matrices using linear-scaling techniques.
  • Helgaker, Trygve (2006). Density-Functional Theory (2h), Basis Sets (3h), Integral Evaluation (2h), Time-Indepent Molecular Properties (3h), Magnetic Properties (4h).
  • Helgaker, Trygve (2006). Hartree-Fock and Kohn-Sham Theories for Large Molecular Systems.
  • Helgaker, Trygve (2006). The right answer for the wrong reason.
  • Helgaker, Trygve (2006). Molecular Magnetic Properties.
  • Helgaker, Trygve (2006). The Rigorous Calculation of Molecular Properties to Chemical Accuracy.
  • Helgaker, Trygve (2006). The Rigorous Calculation of Molecular Properties to Chemical Accuracy.
  • Reine, Simen Sommerfelt & Helgaker, Trygve (2006). Linear Scaling Density-Fitted Coulomb Evaluation.
  • Reine, Simen Sommerfelt & Helgaker, Trygve (2006). Linear Scaling Density-Fitted Coulomb Evaluation.
  • Tellgren, Erik & Helgaker, Trygve (2006). Introducing periodic boundary conditions into a molecular code.
  • Rizzo, Antonio; Cappelli, Chiara; Junquera-Hernández, José Miguel; Sánchez de Merás, Alfredo M. J.; Sánchez-Marín, José & Helgaker, Trygve [Show all 7 contributors for this article] (2006). ELectric and Magnetic Properties of Boron Trihalides.
  • Lutnæs, Ola Berg; Teale, Andrew M.; Helgaker, Trygve & Tozer, David J. (2006). Calculation of rotational g tensors using density functional theory methods.
  • Tellgren, Erik & Helgaker, Trygve (2006). Introducing periodic boundary conditions into a molecular code.
  • Helgaker, Trygve (2005). Computers in chemistry education.
  • Helgaker, Trygve (2005). Density Functional Theory in Quantum Chemistry.
  • Helgaker, Trygve (2005). Geometry optimizations.
  • Helgaker, Trygve (2005). Energy derivatives and molecular properties.
  • Helgaker, Trygve (2005). Molecular Magnetic Properties.
  • Helgaker, Trygve (2005). The exhaustion of the Schrödinger equation: The accurate calculation of molecular properties for light systems.
  • Helgaker, Trygve (2005). The exhaustion of the Schrödinger equation: the accurate calculation of molecular properties for light systems.
  • Helgaker, Trygve (2005). The Accurate Calculation of Molecular Properties with Relativistic Corrections.
  • Coriani, Sonia; Marchesan, Domenico; Gauss, Jurgen; Hattig, Christof; Helgaker, Trygve & Jørgensen, Poul (2005). Accurate geometries from ab initio calculations: Systems containing second-row atoms and transition metals.
  • Helgaker, Trygve (2004). Kjemilab i datamaskinen. [Newspaper]. Apollon.
  • Helgaker, Trygve (2004). Quantum chemistry: quantum-mechanical simulations in chemistry.
  • Helgaker, Trygve (2004). Second Quantization (4h), Density-Functional Theory (2h), Basis Sets (3h), Integral Evaluation (4h), Time-Indepent Molecular Properties (3h), Magnetic Properties (4h).
  • Helgaker, Trygve (2004). Many-Body Methods in Quantum Chemistry.
  • Helgaker, Trygve (2004). The Application of Response Theory to Large Molecular Systems.
  • Helgaker, Trygve (2004). The Accurate Calculation of Harmonic and Fundamental Vibrational Frequencies.
  • Helgaker, Trygve (2004). The Application of Density Functional Response Theory to Large Molecular Systems.
  • Helgaker, Trygve (2004). The Application of Response Theory to Large Molecular Systems.
  • Helgaker, Trygve (2004). The Accurate Calculation of Harmonic and Fundamental Vibrational Frequencies.
  • Sellevåg, Stig Rune; Temps, Friderich; Gripp, Joachim; Robb, Michael A; Stenstrøm, Yngve & Nielsen, Claus Jørgen (2004). An Experimental and Computational Study of the Photolysis of CH3CHO, CH2FCHO, CHF2CHO and CF3CHO.
  • Helgaker, Trygve Ulf (2003). Geometry optimization.
  • Helgaker, Trygve Ulf (2003). Molecular magnetic properties.
  • Helgaker, Trygve Ulf (2003). Energy derivatives and molecular properties.
  • Helgaker, Trygve Ulf (2003). The A Priori Calculation of Molecular Properties to Chemical Accuracy.
  • Bakken, Vebjørn; Helgaker, Trygve Ulf & Uggerud, Einar (2003). Ions - then radicals. Dynamics and mechanisms of electron capture dissociation of proteins and peptides.
  • Helgaker, Trygve Ulf (2003). The Dalton program.
  • Helgaker, Trygve Ulf (2003). The a priori calculation of NMR indirect nuclear spin-spin coupling constants.
  • Helgaker, Trygve Ulf (2003). The calculation of spin-spin coupling constants in large molecules.
  • Bakken, Vebjørn; Helgaker, Trygve Ulf & Uggerud, Einar (2003). Mechanism of Electron Capture Dissociation of Protonated Peptides.
  • Bakken, Vebjørn; Helgaker, Trygve Ulf & Uggerud, Einar (2003). Dynamics of Electron Capture Dissociation of Protonated Peptides.
  • Lutnæs, Ola Berg; Ruden, Torgeir Andersen & Helgaker, Trygve Ulf (2003). The performance of B3LYP for the calculation of indirect NMR spin--spin coupling constants.
  • Helgaker, Trygve Ulf (2002). Energy derivatives and geometry optimization.
  • Hauge, Eirill Strand; Pedersen, Thomas Bondo & Helgaker, Trygve (2021). Extrapolating the Electric Dipole Moment. Universitetet i Oslo, Det matematisk-naturvitenskapelige fakultet.
  • Hansen, Audun Skau; Pedersen, Thomas Bondo; Helgaker, Trygve & Kvaal, Simen (2021). Local correlation methods for infinite systems. Universitetet i Oslo, Det matematisk-naturvitenskapelige fakultet. ISSN 1501-7710. 2021(2380). Full text in Research Archive
  • Skjelstad, Bastian; Balcells, David & Helgaker, Trygve (2020). A Computational Perspective on the Interplay Between Metal Dopant and Support in the Structure and Reactivity of Oxidized Cubanes. Kjemisk Institutt, Universitetet i Oslo.
  • Austad, Jon; Helgaker, Trygve & Tellgren, Erik (2020). Theoretical Investigations of Molecular Electronic Structure in a Magnetic Field. Faculty of Mathematics and Natural Sciences, University of Oslo. ISSN 1501-7710. 2020(2295). Full text in Research Archive
  • Peltzer, Raphael Mathias; Cascella, Michele; Pedersen, Thomas Bondo & Helgaker, Trygve (2018). Multi-scale computational modelling of bio-chemical systems in the condensed phase. Universitetet i Oslo. ISSN 1501-7710. 2018(2058).
  • Miller, Glenn B. S.; Uggerud, Einar & Helgaker, Trygve (2018). Intrinsic Reactivity of Reduced Mg and Zn with CO2 – Relationships to Biological and Non-Biological C–C Bond Formation. Universitetet i Oslo. ISSN 1501-7710. 2018(1976).
  • Trøyflat, Jostein; Helgaker, Trygve; Tellgren, Erik & Reine, Simen Sommerfelt (2015). Efficient methods for self-consistent field calculation of molecules in finite magnetic fields. Universitetet i Oslo.
  • Bunkan, Arne Joakim Coldevin; Nielsen, Claus Jørgen; Uggerud, Einar & Helgaker, Trygve (2015). A theoretical and experimental study of atmospheric reactions of amines and their degradation products. Universitetet i Oslo.
  • Rybkin, Vladimir; Helgaker, Trygve & Uggerud, Einar (2014). Development of Direct Born-Oppenheimer Molecular Dynamics with Applications to Water Clusters and Mechanochemistry. Universitetet i Oslo.
  • Zatula, Alexey; Uggerud, Einar; Helgaker, Trygve & Samdal, Svein (2012). Experimental and computational studies of dynamic processes in ionic water clusters. Universitetet i Oslo.
  • Larsen, Kjersti Beate; Fjellvåg, Helmer; Bakken, Vebjørn; Ponniah, Ravindran & Helgaker, Trygve (2011). DFT-modellering av elektroniske og optiske egenskaper i CPO-27-Zn. Kjemisk institutt, Universitetet i Oslo.
  • Gisler, Galen Ross; Celledoni, Elena; Helgaker, Trygve; Iversen, Trond; Jakobsen, Kjetill Sigurd & Jones, Colin N. [Show all 12 contributors for this article] (2010). The scientific case for eInfrastructure in Norway. The Research Council of Norway. ISSN 978-82-12-02831-9.
  • Lutnæs, Ola Berg; Helgaker, Trygve & Tozer, David J. (2009). Density-functional-theory calculations of second-order magnetic properties. Universitetet i Oslo.
  • Reine, Simen Sommerfelt; Helgaker, Trygve & Pawlowski, Filip (2009). Density functional theory for large molecular systems. Universitetet i Oslo.
  • Tellgren, Erik; Helgaker, Trygve; Ruud, Kenneth & Soncini, Alessandro (2009). Quantum-chemical method development for extended and magnetic systems. Universitetet i Oslo.
  • Strenalyuk, Tatyana; Samdal, Svein & Helgaker, Trygve (2008). Molecular structure of phthalocyanine complexes using gas-phase electron diffraction and quantum chemical calculations. Universitetet i Oslo.
  • Gruber-Stadler, Margret; Nielsen, Claus Jørgen; Helgaker, Trygve & Mühlhäuser, Max (2008). Quantum chemistry studies of elementary atmospheric key reactions. Universitetet i Oslo.
  • Ruden, Torgeir Andersen & Helgaker, Trygve (2004). The accurate calculation of molecular properties and vibrational corrections. Unipub forlag.

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Published Dec. 27, 2021 8:53 PM - Last modified Jan. 12, 2022 5:15 PM