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Helgaker, Trygve
(2024).
Kvantekjemi.
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Helgaker, Trygve
(2024).
Kvantekjemi — på liv og død.
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Helgaker, Trygve
(2024).
Molecular Bonding, Structure, and Dynamics in a Strong Magnetic Field.
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Helgaker, Trygve
(2024).
High-accuracy quantum chemistry.
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Helgaker, Trygve
(2023).
Kvantekjemi.
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Helgaker, Trygve
(2023).
Kvantemekanikk og kjemi.
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Helgaker, Trygve
(2023).
Kvantekjemi.
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Helgaker, Trygve
(2023).
Kvantekjemi — på liv og død.
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Helgaker, Trygve
(2023).
Kvantekjemi — på liv og død.
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Helgaker, Trygve
(2023).
Molecular dynamics and rovibrational spectra in a magnetic field.
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Helgaker, Trygve
(2023).
Molecular dynamics and rovibrational spectra in a magnetic field.
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Hansen, Audun Skau; Helgaker, Trygve & Laestadius, Andre
(2022).
En introduksjon til kvantekjemi / Samarbeid med Talentsenter i realfag.
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Helgaker, Trygve
(2022).
Kvantemekanikk og kjemi.
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Helgaker, Trygve
(2022).
Diversity at the Hylleraas Centre.
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Stenseth, Nils Christian; Andreassen, Karin Marie; Danielsen, Anne; Helgaker, Trygve; Jansen, Eystein & Moser, Edvard Ingjald
[Show all 11 contributors for this article]
(2022).
Grunnforskningen er truet.
Klassekampen.
ISSN 0805-3839.
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Helgaker, Trygve
(2022).
Kvantekjemi—på liv og død.
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Helgaker, Trygve
(2022).
Current-Density-Functional Theory in a Convex Treatment.
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Helgaker, Trygve
(2022).
Molecular Bonding, Structure, and Dynamics in a Strong Magnetic Field.
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Helgaker, Trygve
(2022).
Molecular Bonding, Structure, and Dynamics in a Strong Magnetic Field.
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Helgaker, Trygve
(2022).
The Exotic Chemistry in an Ultrastrong Magnetic Field.
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Dembinski, S.; Karwowski, J.; Szudy, J. & Helgaker, Trygve
(2022).
Foreword.
Molecular Physics.
ISSN 0026-8976.
120(19-20).
doi:
10.1080/00268976.2022.2144060.
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Helgaker, Trygve
(2021).
Forskere på sporet av gammelt mysterium: Slik «ser» trekkfugler magnetfelt.
[Internet].
NRK.
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Helgaker, Trygve
(2021).
Hylleraas-senteret.
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Helgaker, Trygve
(2021).
The Exotic Chemistry in a Strong Magnetic Field.
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Helgaker, Trygve
(2021).
The Exotic Chemistry in an Ultrastrong Magnetic Field.
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Helgaker, Trygve
(2021).
Molecular Dynamics and Rovibrational Spectra in a Strong Magnetic Field.
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Helgaker, Trygve
(2021).
The Exotic Chemistry in a Strong Magnetic Field.
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Tellgren, Erik & Helgaker, Trygve
(2020).
Strong Magnetic Field-Induced Chemical Bonding.
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Helgaker, Trygve
(2020).
Hylleraas Centre for Quantum Molecular Sciences –
Applying For and Setting Up a Centre of Excellence
.
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Helgaker, Trygve
(2020).
SFF V: Assessment Criteria — Applying For and Setting Up a Centre of Excellence.
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Helgaker, Trygve
(2020).
Quantum Chemistry – A Matter of Life and Death.
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Helgaker, Trygve
(2020).
Chemistry in a Strong Magnetic Field.
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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.
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Helgaker, Trygve
(2019).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2019).
Molecules in magnetic fields.
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Helgaker, Trygve
(2019).
Time-independent molecular properties.
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Helgaker, Trygve
(2019).
Geometry optimization.
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Helgaker, Trygve
(2019).
Hylleraas Centre for Quantum Molecular Sciences.
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Helgaker, Trygve
(2019).
Kvantekjemi — på liv og død.
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Helgaker, Trygve
(2019).
Hylleraas Centre for Quantum Molecular Sciences: Applying for and Setting up a Centre of Excellence.
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Helgaker, Trygve
(2019).
Centre for Data Science and Computational Science.
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Helgaker, Trygve
(2019).
Utenomjordisk kjemi.
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Helgaker, Trygve
(2019).
Egil A. Hylleraas – en norsk pioner innen kvantemekanikk.
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Helgaker, Trygve
(2019).
Utenomjordisk kjemi.
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Helgaker, Trygve
(2019).
Kvantemekanikk og kjemi.
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Helgaker, Trygve
(2019).
Kvantemekanikk og kjemi.
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Helgaker, Trygve
(2019).
Kvantemekanikk og kjemi.
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Helgaker, Trygve
(2019).
Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
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Helgaker, Trygve
(2019).
Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
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Helgaker, Trygve
(2019).
Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
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Helgaker, Trygve
(2019).
Chemistry in a Strong Magnetic Field.
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Helgaker, Trygve
(2019).
Egil A. Hylleraas - a pioneer of computational quantum mechanics.
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Helgaker, Trygve
(2019).
Robust All-Electron Optimization of Orbital-Free Density-Functional Theory.
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Helgaker, Trygve
(2019).
Quantum-Chemical Calculations of NMR Parameters.
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Helgaker, Trygve
(2019).
Chemistry in a strong magnetic field.
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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.
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Helgaker, Trygve; Ruud, Kenneth & Røsjø, Bjarne
(2019).
Forskerne ved Hylleraas-senteret jakter på kjemiens hellige gral.
[Newspaper].
Titan.uio.no.
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Helgaker, Trygve; Svelle, Stian & Haugnes, Gunhild Merete
(2019).
Datakraft gir forskerne bedre intuisjon og flere ideer.
[Newspaper].
Titan.uio.no.
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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.
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Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve
(2019).
Guaranteed convergence of a regularized Kohn-Sham iteration in finite dimensions.
Show summary
Guaranteed convergence of a regularized Kohn-Sham iteration in finite dimensions
M. Penz2, A. Laestadius1, E. Tellgren1, M. Ruggenthaler2, S. Kvaal1, T. Helgaker1
1. University of Oslo, Department of Chemistry, Oslo, Germany
2 .Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
The iterative Kohn-Sham scheme [1] has to date not been rigorously shown to converge to the correct ground-state density. This talk addresses the recent result of Penz et al. [2] that demonstrates the convergence of the exact Moreau-Yosida regularized theory in a finite-dimensional setting. This builds on previous work [3], where a similar iterative scheme was proposed that proved a weak type of convergence following an idea by Wagner et al. [4,5]. To obtain the desired convergence in both densities and potentials, the Moreau-Yosida regularization is key for the convergence proof in [2]. This ensures differentiability of the universal Lieb functional [6] and was introduced in density-functional theory (DFT) by Kvaal et al. [7]. It has also recently been successfully applied to paramagnetic current DFT [8].
References
[1] W. Kohn and L.J. Sham, Phys. Rev. 140, A1133 (1965).
[2] M. Penz, A. Laestadius, E.I. Tellgren, and Michael Ruggenthaler, Phys. Rev. Lett. 123, 037401 (2019).
[3] A. Laestadius, M. Penz, E.I. Tellgren, M. Ruggenthaler, S. Kvaal, and T. Helgaker, J. Chem. Phys. 149, 164103 (2018).
[4] L.O. Wagner, E. M. Stoudenmire, K. Burke, and S.R. White, Phys. Rev. Lett. 111, 093003 (2013).
[5] L.O. Wagner, T. E. Baker, E. M. Stoudenmire, K. Burke, and S.R. White, Physical Review B 90, 045109 (2014).
[6] E.H. Lieb, Int. J. Quantum Chem. 24, 243 (1983).
[7] S. Kvaal, U. Ekström, A.M. Teale, and T. Helgaker, J. Chem. Phys. 140, 18A518 (2014).
[8] A. Laestadius, M. Penz, E.I. Tellgren, M. Ruggenthaler, S. Kvaal, and T. Helgaker, J. Chem. Theory Comput. 15, 4003 (2019).
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Tellgren, Erik; Helgaker, Trygve & Sen, Sangita
(2019).
Unifying kinetic energy density and current density in density-functional theory.
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Tellgren, Erik; Helgaker, Trygve & Sen, Sangita
(2019).
Unifying kinetic energy density and current density in density-functional theory.
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Tellgren, Erik; Helgaker, Trygve & Sen, Sangita
(2019).
Unifying kinetic energy density and current density in density-functional theory.
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Helgaker, Trygve
(2018).
Hylleraas Centre for Quantum Molecular Sciences.
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Helgaker, Trygve
(2018).
Closed-Shell Molecular Paramagnetism.
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Helgaker, Trygve
(2018).
Hylleraas Centre for Quantum Molecular Sciences — Ny giv i nytt senter, kvinnelige rollemodeller og nytt initiativ til karrierestøtte, .
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Helgaker, Trygve
(2018).
Utenomjordisk kjemi.
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Helgaker, Trygve
(2018).
Molecular Derivatives and Properties.
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Helgaker, Trygve
(2018).
Four-Way Correspondence of Density-Functional Theory.
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Helgaker, Trygve
(2018).
Chemistry in Strong Magnetic Fields.
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Helgaker, Trygve
(2018).
Kvantemekanikk og kjemi.
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Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen & Helgaker, Trygve
(2018).
Generalized Kohn-Sham iteration on Banach Spaces.
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Helgaker, Trygve
(2017).
Four-Way Correspondence of Density-Functional Theory.
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Helgaker, Trygve
(2017).
Hylleraas Centre.
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Helgaker, Trygve
(2017).
CTCC Review.
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Helgaker, Trygve
(2017).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2017).
Molecules in Magnetic Fields.
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Helgaker, Trygve
(2017).
Time-Dependent Molecular Properties.
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Helgaker, Trygve
(2017).
Geometry Optimization.
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Helgaker, Trygve
(2017).
Quantum Chemistry in Magnetic Fields.
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Helgaker, Trygve
(2017).
Four-Way Correspondence of Density-Functional Theory.
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Helgaker, Trygve
(2017).
Density-Functional Theory in Magnetic Fields.
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Helgaker, Trygve
(2017).
The Role of the Hohenberg-Kohn Theorem in Density-Functional Theory.
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Helgaker, Trygve
(2017).
Density-Functional Theory in Magnetic Fields.
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Helgaker, Trygve
(2017).
Hylleraas Centre for Quantum Molecular Sciences.
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Helgaker, Trygve
(2017).
The Role of the Hohenberg-Kohn Theorem in Density-Functional Theory.
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Helgaker, Trygve
(2017).
Principles of Density-Functional Theory.
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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.
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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.
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Helgaker, Trygve
(2016).
Derivatives and Properties.
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Borgoo, Alex; Tozer, David J.; Teale, Andrew Michael & Helgaker, Trygve
(2016).
Approximate orbital-free non-interacting kinetic energy density functionals from density scaling.
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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.
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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.
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Helgaker, Trygve
(2016).
Molecules in Magnetic Fields.
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Helgaker, Trygve
(2016).
Recent Developments in Current-Density-Functional Theory.
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Helgaker, Trygve
(2016).
The Role of the Hohenberg–Kohn Theorem in Density-Functional Theory.
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Helgaker, Trygve
(2016).
The Role of the Hohenberg–Kohn Theorem in Density-Functional Theory.
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Helgaker, Trygve & Lüthi, Hans Peter
(2016).
Jan Almlöf.
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Helgaker, Trygve
(2016).
Current-Density-Functional Theory of Molecules in Weak and Strong Magnetic Fields.
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Helgaker, Trygve
(2016).
Current-Density-Functional Theory of Molecules in Weak and Strong Magnetic Fields.
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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.
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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.
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Borgoo, Alex; Helgaker, Trygve & Tozer, David J.
(2015).
Exploring homogeneity under density scaling and Molecular binding in post-Kohn–Sham orbital-free DFT
.
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Borgoo, Alex; Teale, Andrew Michael & Helgaker, Trygve
(2015).
Excitation energies from ensemble DFT.
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Borgoo, Alex; Teale, Andrew Michael & Helgaker, Trygve
(2015).
Excitation energies from ensemble DFT.
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Helgaker, Trygve
(2015).
Molecular magnetic properties.
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Helgaker, Trygve
(2015).
Time-Independent molecular properties.
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Helgaker, Trygve
(2015).
Geometry optimisation.
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Helgaker, Trygve
(2015).
Density-functional theory in magnetic fields.
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Helgaker, Trygve
(2015).
Fundamentals of density-functional theory.
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Helgaker, Trygve
(2015).
Density-functional theory in magnetic fields.
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Helgaker, Trygve
(2015).
Egil A. Hylleraas.
-
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Helgaker, Trygve
(2015).
Density-functional theory in magnetic fields.
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Helgaker, Trygve
(2015).
Egil A. Hylleraas.
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Helgaker, Trygve
(2015).
Moreau–Yosida Regularised DFT.
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Helgaker, Trygve
(2015).
Magnetisk binding.
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Helgaker, Trygve
(2015).
Density-Functional Theory in Magnetic Fields
.
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Helgaker, Trygve
(2015).
Exact but Differentiable Formulation of Density-Functional Theory.
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Helgaker, Trygve
(2015).
Exact but Differentiable Formulation of Density-Functional Theory.
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Helgaker, Trygve & Reine, Simen Sommerfelt
(2015).
Fremtidens nanomedisiner bygger på kvantekjemi.
[Journal].
Apollon.
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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.
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Sagvolden, Espen; Tellgren, Erik; Ekström, Ulf Egil & Helgaker, Trygve
(2014).
Cusp based DFT functionals.
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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.
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Helgaker, Trygve
(2014).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2014).
The Molecular Hamiltonian.
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Helgaker, Trygve
(2014).
Time-Independent Molecular Properties.
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Helgaker, Trygve
(2014).
Basis Sets for Electron Correlation.
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Helgaker, Trygve
(2014).
Basis Functions and Basis Sets.
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Helgaker, Trygve
(2014).
Moelcular Integral Evaluation.
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Helgaker, Trygve
(2014).
Density-Functional Theory.
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Teale, Andrew Michael; Furness, James; Tellgren, Erik; Ekström, Ulf Egil & Helgaker, Trygve
(2014).
Density Functional Theory for Molecules in Magnetic Fields.
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Helgaker, Trygve; Hoffmann, Mark; Lange, Kai Kaarvann; Soncini, Alessandro & Tellgren, Erik
(2014).
Molecules in Strong Magnetic Fields.
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Helgaker, Trygve; Kvaal, Simen; Ekström, Ulf Egil & Teale, Andy
(2014).
Differentiable but Exact Formulation of Density-Functional Theory.
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Helgaker, Trygve
(2014).
Beregningskjemi.
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Helgaker, Trygve
(2014).
Quantum-Chemical Calculations of NMR Parameters.
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Helgaker, Trygve; Kvaal, Simen; Ekström, Ulf Egil & Teale, Andrew Michael
(2014).
Differentiable but Exact Formulation of Density-Functional Theory.
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Helgaker, Trygve; Kvaal, Simen; Teale, Andrew Michael; Ekström, Ulf Egil; Jørgensen, Poul & Olsen, Jeppe
(2014).
Differentiable but Exact Formulation of Density-Functional Theory.
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Helgaker, Trygve; Kvaal, Simen; Teale, Andrew Michael & Ekström, Ulf Egil
(2014).
Differentiable but Exact Formulation of Density-Functional Theory.
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Helgaker, Trygve
(2014).
Nobelprisen i kjemi 2013 og noe annet...
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Borgoo, Alex; Teale, Andrew Michael & Helgaker, Trygve
(2014).
Ensemble energies: An alternative route to excitation energies.
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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.
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Stopkowicz, Stella & Helgaker, Trygve
(2014).
Coupled-Cluster Theory for Molecules in Strong Magnetic Fields.
Show summary
In astrochemistry, very strong magnetic fields play an important role. Fields of about 100 T to 100 kT arise around white dwarfs while in neutron stars the fields are even higher (1-100 MT). The interpretation of observed spectra is hampered by the fact that in laboratory measurements magnetic fields can only be produced to up to about 50 T for static fields and to 1000 T in destructive pulse experiments.
Therefore, theoretical investigations may help in understanding the substantial influence of strong magnetic fields on the energies and properties of molecules. Usually, magnetic field-de- pendence in quantum-chemical calculations is treated via a perturbative approach using a Taylor expansion around the field B = 0. Employing a more rigorous treatment, however, enables the study of molecules in finite fields of arbitrary strength and led to findings showing distinctly mod- ified chemical properties in very strong fields such as a paramagnetic-to-diamagnetic transition for closed-shell molecules [1] and a new paramagnetic bonding mechanism in diatomics [2].
In this work, coupled-cluster capabilities are introduced to the LONDON program which treats the magnetic field in a non-perturbative manner and uses London orbitals (GIAOs) in order to ensure gauge-origin invariance. As Full-CI results indicate an increasing single-reference character for higher field-strengths, the performance of truncated coupled-cluster approaches is expected to be advantageous. We will present results for energies and magnetizabilities, thereby investigating the influence of field-strengths, electron-correlation, and the use of GIAOs.
[1] E. I. Tellgren, T. Helgaker, and A. Soncini, Phys. Chem. Chem. Phys., 11, 5489, (2009). [2] K. K. Lange, E. I. Tellgren, M. R. Hoffmann, and T. Helgaker, Science, 337, 327, (2012).
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Sagvolden, Espen; Tellgren, Erik; Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve
(2013).
Building blocks of Current Density Functional Theory.
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Sagvolden, Espen; Tellgren, Erik; Kvaal, Simen; Ekström, Ulf Egil; Teale, Andrew Michael & Helgaker, Trygve
(2013).
Building blocks of Current Density Functional Theory.
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Ekström, Ulf Egil; Kvaal, Simen; Borgoo, Alex; Helgaker, Trygve; Sagvolden, Espen & Tellgren, Erik
(2013).
Moreau-Yosida regularization of DFT.
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Kvaal, Simen; Ekström, Ulf Egil; Tellgren, Erik; Borgoo, Alex; Helgaker, Trygve & Sagvolden, Espen
(2013).
Moreau-Yosida regularization of DFT.
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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.
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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.
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Stopkowicz, Stella & Helgaker, Trygve
(2013).
Correlated molecular energies in strong magnetic fields.
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Pedersen, Thomas Bondo; Rekkedal, Johannes Andreas; Iozzi, Maria Francesca; Coriani, Sonia; Teale, Andrew Michael & Helgaker, Trygve
(2013).
Molecular Properties in the Random Phase Approximation.
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Helgaker, Trygve
(2013).
Molecular magnetism and density-functional theory in magnetic fields.
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Helgaker, Trygve
(2013).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2013).
Molecules in Strong Magnetic Fields.
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Helgaker, Trygve
(2013).
Metoder i teoretisk og beregningsorientert kjemi / Kvantekjemiske beregninger i moderne kjemisk forskning,
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Helgaker, Trygve
(2013).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2013).
Nobel Prize 2013.
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Helgaker, Trygve
(2013).
Molecular magnetic properties.
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Helgaker, Trygve
(2013).
TIme-independet molecular properties.
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Helgaker, Trygve
(2013).
Geometry optimization.
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Helgaker, Trygve
(2013).
Molecular magnetism and density-functional theory in magnetic fields.
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Helgaker, Trygve
(2013).
Molecular Magnetism and Density-Functional Theory in Magnetic Fields.
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Helgaker, Trygve
(2013).
Molecules in Strong Magnetic Fields.
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Helgaker, Trygve
(2013).
Molecular magnetism and density-functional theory in magnetic fields.
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Helgaker, Trygve
(2013).
Density-functional theory, with and without a magnetic field.
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Gauss, Jurgen; Helgaker, Trygve & Stanton, John F.
(2012).
Foreword.
Molecular Physics.
ISSN 0026-8976.
110,
p. 2313–2313.
doi:
10.1080/00268976.2012.731766.
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Helgaker, Trygve
(2012).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2012).
Current-density-functional theory: basic variables and convex conjugation.
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Helgaker, Trygve
(2012).
Magnetic resonance parameteres.
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Helgaker, Trygve
(2012).
Molecules in an external magnetic field.
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Helgaker, Trygve
(2012).
The electronic Hamiltonian.
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Helgaker, Trygve
(2012).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2012).
Time-independent molecular properties.
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Helgaker, Trygve
(2012).
Geometry optimization.
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Helgaker, Trygve
(2012).
Basis sets for electron correlation.
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Helgaker, Trygve
(2012).
Basis functions and basis sets.
-
Helgaker, Trygve
(2012).
High-accuracy quantum chemistry.
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Helgaker, Trygve
(2012).
Chemical bonding in strong magnetic fields.
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Helgaker, Trygve
(2012).
Molecular magnetic propeties.
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Helgaker, Trygve
(2012).
The molecular Hamiltonian.
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Helgaker, Trygve
(2012).
Time-independent molecular properties.
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Helgaker, Trygve
(2012).
Molecular integral evaluation.
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Helgaker, Trygve
(2012).
Basis sets for electron correlation.
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Helgaker, Trygve
(2012).
Basis functions and basis sets.
-
Helgaker, Trygve
(2012).
Density-functional theory.
-
Helgaker, Trygve
(2012).
Chemical bonding in strong magnetic fields.
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Helgaker, Trygve
(2012).
Molecular bonding in strong magnetic fields.
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Helgaker, Trygve
(2012).
Density-functional theory in magnetic fields.
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Helgaker, Trygve
(2012).
Kvantekmekanikk på datamaskiner: kjemiens nye verktøy.
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Helgaker, Trygve
(2012).
Density-functional theory in magnetic fields.
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Helgaker, Trygve
(2011).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2011).
Molecular Electronic-Structure Theory: Yesterday, Today and Tomorrow.
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Helgaker, Trygve
(2011).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2011).
Quantum chemistry: wave-function and density-functional methods.
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Helgaker, Trygve
(2011).
Importing ab-initio theory into DFT. some applications of the Lieb variation principle.
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Helgaker, Trygve
(2011).
Kvantemekanikk på datamaskiner: kjemiens nye verktøy.
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Helgaker, Trygve
(2011).
Centre for Theoretical and Computational Chemistry.
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Helgaker, Trygve
(2011).
Kvantemekanikk på datamaskiner: kjemiens nye verktøy.
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Helgaker, Trygve
(2011).
Kvantemekanikk på datamaskiner: kjemiens nye verktøy.
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Helgaker, Trygve
(2011).
Molecular bonding in strong magnetic fields.
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Helgaker, Trygve
(2011).
Molecular electronic structure in strong magnetic fields.
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Helgaker, Trygve
(2011).
Molecules in strong magnetic fields: electron correlation.
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Helgaker, Trygve
(2011).
Geometry Optimization.
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Helgaker, Trygve
(2011).
TIme-independent molecular properties.
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Helgaker, Trygve
(2011).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2011).
Molecules in strong magnetic fields: electron correlation.
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Helgaker, Trygve
(2011).
Molecular electronic-structure theory; some current trends.
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Helgaker, Trygve
(2011).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2011).
Molecules in strong magnetic fields.
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Helgaker, Trygve; Kaarvann, Lange Kai & Tellgren, Erik
(2011).
Molecules in strong magnetic fields.
META.
ISSN 1890-1956.
p. 16–18.
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Helgaker, Trygve
(2010).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2010).
The Molecular Hamiltonian.
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Helgaker, Trygve
(2010).
Time-Independent Molecular Properties.
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Helgaker, Trygve
(2010).
Basis Sets for Electron Correlation.
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Helgaker, Trygve
(2010).
Basis Functions and Basis Sets.
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Helgaker, Trygve
(2010).
Molecular Integral Evaluation.
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Helgaker, Trygve
(2010).
Density-functional theory.
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Helgaker, Trygve
(2010).
The exhaustion of the Schrodinger equation: The accurate calculation of molecular properties of light systems.
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Helgaker, Trygve
(2010).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2010).
Geometry optimization.
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Helgaker, Trygve
(2010).
Computational Chemistry.
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Helgaker, Trygve
(2010).
The calculation of the universal density functional by Lieb maximization.
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Helgaker, Trygve
(2010).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2010).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2010).
Ab initio studies for the adiabatic connection in density-functional theory.
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Helgaker, Trygve
(2010).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2010).
Convergence properties of the coupled-cluster method: the accurate calculation of molecular properties for light systems.
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Helgaker, Trygve
(2010).
The rigorous calculation of the universal density functional by the Lieb variation principle.
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Helgaker, Trygve
(2010).
Rigorous calculation of the universal density functional by the Lieb variation principle.
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Helgaker, Trygve
(2010).
Ab-initio studies of the adiabatic connection in density-functional teory.
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Helgaker, Trygve
(2010).
Calculation and Modeling of Adiabatic-Connection Curves.
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Helgaker, Trygve
(2009).
From ab initio methods to density-functional theory.
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Helgaker, Trygve
(2009).
Geometry Optimization.
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Helgaker, Trygve
(2009).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2009).
Time-Independent Molecular Properties.
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Helgaker, Trygve
(2009).
The Adiabatic Connection.
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Helgaker, Trygve
(2009).
Linear-Scaling Methods for Molecular Energies and Properties.
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Helgaker, Trygve
(2009).
The Generalized Adiabatic Connection.
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Helgaker, Trygve
(2009).
Computational Chemistry.
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Helgaker, Trygve
(2008).
Molecules in strong magnetic fields.
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Helgaker, Trygve
(2008).
Organic Quantum Chemistry.
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Helgaker, Trygve
(2008).
Molecules in Strong Magnetic Fields.
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Helgaker, Trygve
(2008).
New Techniques of Self-Consistent Field Theory.
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Helgaker, Trygve
(2008).
The Dalton Quantum-Chemistry Program: Current Capabilities and Ongoing Developments.
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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).
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Helgaker, Trygve
(2008).
Methods for the calculation of internal and external perturbations of molecular systems.
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Helgaker, Trygve
(2008).
The development of methods for the calculation of the response of molecular systems to internal and external perturbations.
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Helgaker, Trygve
(2008).
Density-functional theory in quantum chemistry.
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Helgaker, Trygve
(2008).
Excitation energies from density-functional theory: some failures and successes.
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Helgaker, Trygve
(2008).
The accurate calculation of molecular energies and properties: A tour of high-accuracy quantum-chemical methods.
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Helgaker, Trygve
(2008).
The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
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Helgaker, Trygve
(2008).
The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
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Helgaker, Trygve
(2008).
The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
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Helgaker, Trygve
(2008).
The application of quantum chemistry to large systems: new techniques of self-consistent field theory.
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Helgaker, Trygve
(2008).
The accurate calculation of molecular energies and properties: a tour of high-accuracy quantum-chemical mthods.
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Helgaker, Trygve
(2008).
The Exhaustion of the Schrodinger equation: The accurate calculation of Molecular Properties of Light Systems.
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Helgaker, Trygve
(2008).
Centre for Theoretical and Computational Chemistry.
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Helgaker, Trygve
(2007).
New techniques of self-consistent field theory.
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Helgaker, Trygve
(2007).
Quantative Quantum Chemistry.
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Helgaker, Trygve
(2007).
Quantum chemistry - a quantitative tool in chemistry.
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Helgaker, Trygve
(2007).
New techniques of self-consistent field theory.
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Helgaker, Trygve
(2007).
Strategies for large-scale molecular self-consistent field calculations.
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Helgaker, Trygve
(2007).
Explicit electron correlation by a combined use of Gaussian-type orbitals and Gaussian-type geminals.
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Helgaker, Trygve
(2007).
Accurate Calculations and Calibration.
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Helgaker, Trygve
(2007).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2007).
Time-Independent Molecular Properites.
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Helgaker, Trygve
(2007).
Geomtry Optimization.
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Helgaker, Trygve
(2007).
Expilcit correlation by a combined use of Gaussian-type orbitals and Gaussian-type geminals.
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Helgaker, Trygve
(2007).
The calculation of energies and properties of large systems.
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Helgaker, Trygve
(2007).
Highly accurate quantum-chemical calculations.
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Helgaker, Trygve; Helgaker, Trygve; Dahle, Pål; Jonsson, Dan & Taylor, Peter R.
(2007).
Quantum-chemical calculations with Gaussian-type orbital and geminal basis sets.
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Helgaker, Trygve
(2007).
The Calculation of Mocular Properties of Large Systems.
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Helgaker, Trygve
(2007).
Relativistic Corrections in Highly Accurate Calculations on Small Molecular Systems.
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Helgaker, Trygve
(2007).
The Right Answer for the Right Reason: A Tour of High-Accuracy Quantum-Chemical Calculations.
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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.
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Helgaker, Trygve
(2007).
Det virtuelle kjemilaboratoriet.
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Helgaker, Trygve
(2007).
Centre for Theoretical and Computational Chemistry.
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Helgaker, Trygve
(2007).
Kvantekjemi - kjemiens nye verktøy.
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Helgaker, Trygve
(2006).
SCF methods for energies and properties of large molecular systems.
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Helgaker, Trygve
(2006).
Self-consistent field methods for large molecular systems.
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Helgaker, Trygve
(2006).
Methods for Hartree-Fock and Kohn-Sham calculations on large molecular systems.
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Helgaker, Trygve
(2006).
Evaluation of Fock/Kohn-Sham matrices using linear-scaling techniques.
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Helgaker, Trygve
(2006).
Density-Functional Theory (2h), Basis Sets (3h), Integral Evaluation (2h), Time-Indepent Molecular Properties (3h), Magnetic Properties (4h).
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Helgaker, Trygve
(2006).
Hartree-Fock and Kohn-Sham Theories for Large Molecular Systems.
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Helgaker, Trygve
(2006).
The right answer for the wrong reason.
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Helgaker, Trygve
(2006).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2006).
The Rigorous Calculation of Molecular Properties to Chemical Accuracy.
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Helgaker, Trygve
(2006).
The Rigorous Calculation of Molecular Properties to Chemical Accuracy.
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Reine, Simen Sommerfelt & Helgaker, Trygve
(2006).
Linear Scaling Density-Fitted Coulomb Evaluation.
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Reine, Simen Sommerfelt & Helgaker, Trygve
(2006).
Linear Scaling Density-Fitted Coulomb Evaluation.
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Tellgren, Erik & Helgaker, Trygve
(2006).
Introducing periodic boundary conditions into a molecular code.
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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.
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Lutnæs, Ola Berg; Teale, Andrew M.; Helgaker, Trygve & Tozer, David J.
(2006).
Calculation of rotational g tensors using density functional theory methods.
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Tellgren, Erik & Helgaker, Trygve
(2006).
Introducing periodic boundary conditions into a molecular code.
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Helgaker, Trygve
(2005).
Computers in chemistry education.
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Helgaker, Trygve
(2005).
Density Functional Theory in Quantum Chemistry.
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Helgaker, Trygve
(2005).
Geometry optimizations.
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Helgaker, Trygve
(2005).
Energy derivatives and molecular properties.
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Helgaker, Trygve
(2005).
Molecular Magnetic Properties.
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Helgaker, Trygve
(2005).
The exhaustion of the Schrödinger equation: The accurate calculation of molecular properties for light systems.
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Helgaker, Trygve
(2005).
The exhaustion of the Schrödinger equation: the accurate calculation of molecular properties for light systems.
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Helgaker, Trygve
(2005).
The Accurate Calculation of Molecular Properties with Relativistic Corrections.
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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.
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Helgaker, Trygve
(2004).
Kjemilab i datamaskinen.
[Newspaper].
Apollon.
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Jestilä, Joakim Samuel; Uggerud, Einar & Helgaker, Trygve
(2021).
Reductive gas-phase ion chemistry of simple oxocarbons in the presence of alkali and alkaline earth metals.
Universitetet i Oslo, Det matematisk-naturvitenskapelige fakultet.
ISSN 1501-7710.
2021(2430).
Show summary
In a circular carbon economy, carbon dioxide (CO2) is recycled and used as a molecular building block to make fuels, chemicals and materials, driven by renewable energy sources. Hence, the molecule represents a potential replacement for oil, natural gas and coal as one of the primary sources of carbon.
A major bottleneck stems from the fact that CO2 requires activation before it can be converted. This work explores the activation and reduction of CO2 by the alkali metal and alkaline earth metal chloride anions on a fundamental level. It sheds light on relevant factors in the conversion of CO2 to valuable products such as oxalate (C2O42−) and carbon monoxide (CO), as well as further conversion of the latter. The aforementioned processes proceed via metal-CO2 intermediates—chemical species formed during conversion of reactants to products—and this thesis links their properties to the extent of CO2 activation. Specifically, more complete electron transfer from the metal to CO2 and larger structural changes in the intermediates are associated with lower energetic demands for further reaction and conversion. These results could prove useful for the development of efficient CO2-recycling processes.
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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
Show summary
Quantum Chemistry constitutes an extensive framework for accurately simulating the electronic wavefunction of atoms and molecules. The same framework may in principle be applied to the domain of periodic structures such as crystals, but is in practice severely limited by the infinite nature of these structures in conjunction with the computational complexity of quantum chemical methods. In his thesis, the candidate utilizes a mathematical structure known as bi-infinite block-Toeplitz matrices in order to smoothly transition between the molecular and periodic realm. Furthermore, he extends the divide-expand-consolidate methods originally devised for molecules to the periodic case, and demonstrates that this procedure can reduce the computational scaling of the simulation while retaining systematic control over the error.
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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
Show summary
Most available literature on molecular systems in magnetic fields are limited to special cases: Either small or highly symmetric species of specific orientation to the field, or fields of low intensity - or combinations of the above.
This dissertation is devoted to the development, implementation, calibration, analysis and usage of computational quantum chemistry methods that are freed from such restrictions. Three research papers are presented. One deals with the inner workings of a generalized variant of Density Functional Theory which allows the magnetic field to be directly included (BDFT), and explores in depth how various functionals handle diamagnetic, paramagnetic and aromatic molecules. The second paper investigates the rich chemistry of the helium dimer in a strong magnetic field, thoroughly maps out the electronic structure of the molecule, and presents the many different magnetic bonding mechanisms and interactions that exist in this regime. The final paper revolves around application of highly accurate wave-function methods to determine the influence of terrestrially available magnetic fields on water. The work of this thesis presents important contributions to theoretical chemistry in the pres-
ence of magnetic fields.
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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.
Show summary
Fulltekst:
http://www.forskningsradet.no/servlet/Satellite?blobcol=urldata&blobheader=application%2Fpdf&blobheadername1=Content-Disposition%3A&blobheadervalue1=+attachment%3B+filename%3DeSOP-The-Scientific-Case-for-eInfrastructure-in-Norway-final%5B1%5D.pdf&blobkey=id&blobtable=MungoBlobs&blobwhere=1274464831935&ssbinary=true
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Ruden, Torgeir Andersen & Helgaker, Trygve
(2004).
The accurate calculation of molecular properties and vibrational corrections.
Unipub forlag.