Simen Reine

• Mikkelsen, Jonas E. S.; Reine, Simen; Pedersen, Thomas B. & Jensen, Frank (2026). Extending Atom–Atom Polarizabilities to Frequency-Dependent Coupled Cluster and MCSCF Response. Journal of Chemical Theory and Computation. ISSN 1549-9618. 22(14), s. 7217–7229. doi: 10.1021/acs.jctc.6c00903. Fulltekst i vitenarkiv Vis sammendrag

  The methodology for calculating distributed atom–atom polarizabilities within the minimal basis iterative Stockholder partitioning framework is extended to coupled cluster (CC2, CCSD, CC3) and multiconfigurational self-consistent field (MCSCF) wave functions, as well as to frequency-dependent perturbations. The bond capacity, defined as the rank-0 atom–atom polarizability, is benchmarked on small molecules at equilibrium geometries, where various DFT functionals show good agreement with the CC3 reference. The same conclusion holds when probing geometry dependence through a change in the bond angle or dihedral angle, but a significant deviation is observed between the methods for reaction pathways such as SN2. The MCSCF implementation is used to study the values for bond breaking, where the rank-0 contribution to the molecular dipole polarizability is found to dominate for various systems. Non-nuclear sites for describing out-of-plane polarizability at the charge-only level are also explored but found to be ineffective with ab initio-derived parameters. Dynamic bond capacities at real and imaginary frequencies are presented and display method dependence consistent with that of the static values.

• Cezar, Henrique Musseli; Bodenstein, Tilmann; Sveinsson, Henrik Andersen; Ledum, Morten; Reine, Simen & Bore, Sigbjørn Løland (2025). Learning atomic forces from uncertainty-calibrated adversarial attacks. npj Computational Materials. 11. doi: 10.1038/s41524-025-01703-5. Fulltekst i vitenarkiv Vis sammendrag

  Adversarial approaches, which intentionally challenge machine learning models by generating difficult examples, are increasingly being adopted to improve machine learning interatomic potentials (MLIPs). While already providing great practical value, little is known about the actual prediction errors of MLIPs on adversarial structures and whether these errors can be controlled. We propose the Calibrated Adversarial Geometry Optimization (CAGO) algorithm to discover adversarial structures with user-assigned errors. Through uncertainty calibration, the estimated uncertainty of MLIPs is unified with real errors. By performing geometry optimization for calibrated uncertainty, we reach adversarial structures with the user-assigned target MLIP prediction error. Integrating with active learning pipelines, we benchmark CAGO, demonstrating stable MLIPs that systematically converge structural, dynamical, and thermodynamical properties for liquid water and water adsorption in a metal-organic framework within only hundreds of training structures, where previously many thousands were typically required.

• Kneiding, Hannes; Lukin, Ruslan; Lang, Lucas; Reine, Simen; Pedersen, Thomas Bondo & Bin, Riccardo De [Vis alle 7 forfattere av denne artikkelen] (2023). Deep learning metal complex properties with natural quantum graphs. Digital Discovery. 2(3), s. 618–633. doi: 10.1039/d2dd00129b. Fulltekst i vitenarkiv Vis sammendrag

  Machine learning can make a strong contribution to accelerating the discovery of transition metal complexes (TMC). These compounds will play a key role in the development of new technologies for which there is an urgent need, including the production of green hydrogen from renewable sources. Despite the recent developments in machine learning for drug discovery and organic chemistry in general, the application of these methods to TMCs remains challenged by their higher complexity and the limited availability of large datasets. In this work, we report a representation for deep graph learning on TMCs – the natural quantum graph (NatQG), which leverages the electronic structure data available from natural bond orbital (NBO) analysis. This data was used to define both the topology and the information expressed by the NatQG graphs. At the topology level, two different NatQG flavors were developed: u-NatQG, with undirected edges, and d-NatQG, with edges directed along donor → acceptor orbital interactions. At the information level, the node and edge attribute vectors of both graphs contain NBO data, including natural charges and bond orders. The NatQG graphs were used to develop graph neural networks (GNNs) for the prediction of the quantum properties underlying the structure and reactivity of TMCs (e.g. HOMO–LUMO gap and polarizability). These models surpassed baselines based on traditional descriptors and performed at a level similar to, or higher than, state-of-the-art GNNs based on radial cutoffs. The results showed that the electronic structure information encoded by the models has a stronger impact on its accuracy than the geometric information. With the aim of benchmarking the GNNs, we also developed the transition metal quantum mechanics graph dataset (tmQMg), which provides the geometries, properties, and NatQG graphs of 60k TMCs.

• Dundas, Karen Oda Hjorth; Beerepoot, Maarten; Ringholm, Magnus; Reine, Simen Sommerfelt; Bast, Radovan & List, Nanna Holmgaard [Vis alle 9 forfattere av denne artikkelen] (2021). Harmonic Infrared and Raman Spectra in Molecular Environments Using the Polarizable Embedding Model. Journal of Chemical Theory and Computation. ISSN 1549-9618. 17(6), s. 3599–3617. doi: 10.1021/acs.jctc.0c01323. Fulltekst i vitenarkiv Vis sammendrag

  We present a fully analytic approach to calculate infrared (IR) and Raman spectra of molecules embedded in complex molecular environments modeled using the fragment-based polarizable embedding (PE) model. We provide the theory for the calculation of analytic second-order geometric derivatives of molecular energies and first-order geometric derivatives of electric dipole moments and dipole–dipole polarizabilities within the PE model. The derivatives are implemented using a general open-ended response theory framework, thus allowing for an extension to higher-order derivatives. The embedding-potential parameters used to describe the environment in the PE model are derived through first-principles calculations, thus allowing a wide variety of systems to be modeled, including solvents, proteins, and other large and complex molecular environments. Here, we present proof-of-principle calculations of IR and Raman spectra of acetone in different solvents. This work is an important step toward calculating accurate vibrational spectra of molecules embedded in realistic environments.

• Olsen, Jógvan Magnus Haugaard; Reine, Simen Sommerfelt; Vahtras, Olav; Kjellgren, Erik; Reinholdt, Peter & Dundas, Karen O.H [Vis alle 25 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  The <i>Dalton Project</i> provides a uniform platform access to the underlying full-fledged quantum chemistry codes Dalton and LSDalton as well as the PyFraME package for automatized fragmentation and parameterization of complex molecular environments. The platform is written in Python and defines a means for library communication and interaction. Intermediate data such as integrals are exposed to the platform and made accessible to the user in the form of NumPy arrays, and the resulting data are extracted, analyzed, and visualized. Complex computational protocols that may, for instance, arise due to a need for environment fragmentation and configuration-space sampling of biochemical systems are readily assisted by the platform. The platform is designed to host additional software libraries and will serve as a hub for future modular software development efforts in the distributed Dalton community.

• Kumar, Chandan; Fliegl, Heike; Jensen, Frank; Teale, Andrew Michael; Reine, Simen Sommerfelt & Kjærgaard, Thomas (2018). Accelerating Kohn‐Sham response theory using density fitting and the auxiliary‐density‐matrix method. International Journal of Quantum Chemistry. ISSN 0020-7608. 118(16), s. 1–21. doi: 10.1002/qua.25639. Fulltekst i vitenarkiv Vis sammendrag

  An extension of the formulation of the atomic‐orbital‐based response theory of Larsen et al., JCP 113, 8909 (2000) is presented. This new framework has been implemented in LSDalton and allows for the use of Kohn‐Sham density‐functional theory with approximate treatment of the Coulomb and Exchange contributions to the response equations via the popular resolution‐of‐the‐identity approximation as well as the auxiliary‐density matrix method (ADMM). We present benchmark calculations of ground‐state energies as well as the linear and quadratic response properties: vertical excitation energies, polarizabilities, and hyperpolarizabilities. The quality of these approximations in a range of basis sets is assessed against reference calculations in a large aug‐pcseg‐4 basis. Our results confirm that density fitting of the Coulomb contribution can be used without hesitation for all the studied properties. The ADMM treatment of exchange is shown to yield high accuracy for ground‐state and excitation energies, whereas for polarizabilities and hyperpolarizabilities the performance gain comes at a cost of accuracy. Excitation energies of a tetrameric model consisting of units of the P700 special pigment of photosystem I have been studied to demonstrate the applicability of the code for a large system.

• Wirz, Lukas Nico; Reine, Simen Sommerfelt & Pedersen, Thomas Bondo (2017). On Resolution-of-the-Identity Electron Repulsion Integral Approximations and Variational Stability. Journal of Chemical Theory and Computation. ISSN 1549-9618. 13(10), s. 4897–4906. doi: 10.1021/acs.jctc.7b00801. Fulltekst i vitenarkiv Vis sammendrag

  The definiteness of the Mulliken and Dirac electron repulsion integral (ERI) matrices is examined for different classes of resolution-of-the-identity (RI) ERI approximations with particular focus on local fitting techniques. For global RI, robust local RI, and nonrobust local RI we discuss the definiteness of the approximated ERI matrices as well as the resulting bounds of Hartree, exchange, and total energies. Lower bounds of Hartree and exchange energy contributions are crucial as their absence may lead to variational instabilities, causing severe convergence problems or even convergence to a spurious state in self-consistent-field optimizations. While the global RI approximation guarantees lower bounds of Hartree and exchange energies, local RI approximations are generally unbounded. The robust local RI approximation guarantees a lower bound of the exchange energy but not of the Hartree energy. The nonrobust local RI approximation guarantees a lower bound of the Hartree energy but not of the exchange energy. These issues are demonstrated by sample calculations on carbon dioxide and benzene using the pair atomic RI approximation. © 2017 American Chemical Society

• Baudin, Pablo; Ettenhuber, Patrick; Reine, Simen Sommerfelt; Kristensen, Kasper & Kjærgaard, Thomas (2016). Efficient linear-scaling second-order Møller-Plesset perturbation theory: The divide-expand-consolidate RI-MP2 model. Journal of Chemical Physics. ISSN 0021-9606. 144(5). doi: 10.1063/1.4940732. Fulltekst i vitenarkiv
• Wang, Yang Min; Hattig, Christof; Reine, Simen Sommerfelt; Valeev, Edward; Kjærgaard, Thomas & Kristensen, Kasper (2016). Explicitly correlated second-order Møller-Plesset perturbation theory in a Divide-Expand-Consolidate (DEC) context. Journal of Chemical Physics. ISSN 0021-9606. 144(20). doi: 10.1063/1.4951696. Fulltekst i vitenarkiv
• 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, s. 3514–3522. doi: 10.1021/acs.jctc.6b00074. Fulltekst i vitenarkiv
• 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, s. 5466–5473. doi: 10.1039/C4CP05246C. Fulltekst i vitenarkiv
• Samdal, Svein; Møllendal, Harald; Reine, Simen Sommerfelt & Guillemin, Jean-Claude (2015). Ring planarity problem of 2-oxazoline revisited using microwave spectroscopy and quantum chemical calculations. Journal of Physical Chemistry A. ISSN 1089-5639. 119(20), s. 4875–4884. doi: 10.1021/acs.jpca.5b02528. Fulltekst i vitenarkiv Vis sammendrag

  In a previous infrared, Raman and microwave spectroscopic work,1 it was claimed that 2-oxazoline has a planar ring equilibrium conformation and the ring-puckering potential function V(z) = 22.2(z4 + 1.31z2)cm‒1, where z is a dimensionless reduced coordinate, was derived. This function reproduces poorly the rotational constants of the lowest and decisive puckering states. The microwave spectrum has been reinvestigated and largely extended to include more than 4600 transitions of the ground state and six excited states of the ring-puckering vibration allowing accurate centrifugal distortion constants to be obtained for the first time. A new potential function V(z) = 38.8(z4 ‒ 0.65z2)cm‒1 has been determined. This function yields much better agreement between calculated and observed rotational constants, especially for the lowest puckering states, than the previous function and predicts a nonplanar ring equilibrium conformation. The barrier to ring planarity is determined to be 49(8) J/mol. The ground-state energy level is 35 cm‒1 above the barrier maximum. Theory predicts that three of the five Watson centrifugal distortion constants, JK, K, and K should vary with the puckering state, whereas J and J should be unaffected. It was found that JK and K indeed behave in the expected manner, while deviations were seen for the three other centrifugal distortion constants. The ab initio methods HF, MP2, CCSD, CCSD(T), CCSD(T)-F12 with large basis sets as well as several DFT methods were used in an attempt to reproduce the low experimental barrier to planar ring. Only the MP2 method yielded a satisfactory prediction of the barrier. The CCSD and the CCSD(T) calculations predict a planar ring, whereas the energy differences between a planar and a nonplanar ring obtained in the CCSD(T)-F12 computations are so small that a definite conclusion cannot be drawn

• Bugeanu, Monica; Remigio, Roberto Di; Mozgawa, Krzysztof; Reine, Simen Sommerfelt; Harbrecht, Helmut & Frediani, Luca (2015). Wavelet formulation of the polarizable continuum model. II. Use of piecewise bilinear boundary elements. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 17(47), s. 31566–31581. doi: 10.1039/c5cp03410h. Fulltekst i vitenarkiv Vis sammendrag

  The simplicity of dielectric continuum models has made them a standard tool in almost any Quantum Chemistry (QC) package. Despite being intuitive from a physical point of view, the actual electrostatic problem at the cavity boundary is challenging: the underlying boundary integral equations depend on singular, long-range operators. The parametrization of the cavity boundary should be molecular-shaped, smooth and differentiable. Even the most advanced implementations, based on the integral equation formulation (IEF) of the polarizable continuum model (PCM), generally lead to working equations which do not guarantee convergence to the exact solution and/or might become numerically unstable in the limit of large refinement of the molecular cavity (small tesserae). This is because they generally make use of a surface parametrization with cusps (interlocking spheres) and employ collocation methods for the discretization (point charges). Wavelets on a smooth cavity are an attractive alternative to consider: for the operators involved, they lead to highly sparse matrices and precise error control. Moreover, by making use of a bilinear basis for the representation of operators and functions on the cavity boundary, all equations can be differentiated to enable the computation of geometrical derivatives. In this contribution, we present our implementation of the IEFPCM with bilinear wavelets on a smooth cavity boundary. The implementation has been carried out in our module PCMSolver and interfaced with LSDalton, demonstrating the accuracy of the method both for the electrostatic solvation energy and for linear response properties. In addition, the implementation in a module makes our framework readily available to any QC software with minimal effort.

• 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. Fulltekst i vitenarkiv
• Aidas, Kestutis; Angeli, Celestino; Bak, Keld L.; Bakken, Vebjørn; Bast, Radovan & Boman, Linus [Vis alle 84 forfattere av denne artikkelen] (2014). The Dalton quantum chemistry program system. Wiley Interdisciplinary Reviews. Computational Molecular Science. ISSN 1759-0876. 4(3). doi: 10.1002/wcms.1172. Fulltekst i vitenarkiv Vis sammendrag

  Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree–Fock, Kohn–Sham, multiconfigurational self-consistent-field, Møller–Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from http://www.daltonprogram.org for a number of UNIX platforms.

• Rybkin, Vladimir; Simakov, Anton; Bakken, Vebjørn; Reine, Simen Sommerfelt; Kjærgaard, Thomas & Helgaker, Trygve [Vis alle 7 forfattere av denne artikkelen] (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), s. 533–544. doi: 10.1002/jcc.23162. Fulltekst i vitenarkiv
• Kristensen, Kasper; Kjærgaard, Thomas; Høyvik, Ida-Marie; Ettenhuber, Patrick; Jørgensen, Poul & Jansik, Branislav [Vis alle 8 forfattere av denne artikkelen] (2013). The divide-expand-consolidate MP2 scheme goes massively parallel. Molecular Physics. ISSN 0026-8976. 111(9-11), s. 1196–1210. doi: 10.1080/00268976.2013.783941. Fulltekst i vitenarkiv
• Merlot, Patrick; Kjærgaard, Thomas; Helgaker, Trygve; Lindh, Roland; Aquilante, Francesco & Reine, Simen Sommerfelt [Vis alle 7 forfattere av denne artikkelen] (2013). Attractive electron-electron interactions within robust local fitting approximations. Journal of Computational Chemistry. ISSN 0192-8651. 34(17), s. 1486–1496. doi: 10.1002/jcc.23284. Fulltekst i vitenarkiv Vis sammendrag

  An analysis of Dunlap's robust fitting approach reveals that the resulting two-electron integral matrix is not manifestly positive semidefinite when local fitting domains or non-Coulomb fitting metrics are used. We present a highly local approximate method for evaluating four-center two-electron integrals based on the resolution-of-the-identity (RI) approximation and apply it to the construction of the Coulomb and exchange contributions to the Fock matrix. In this pair-atomic resolution-of-the-identity (PARI) approach, atomic-orbital (AO) products are expanded in auxiliary functions centered on the two atoms associated with each product. Numerical tests indicate that in 1% or less of all Hartree-Fock and Kohn-Sham calculations, the indefinite integral matrix causes nonconvergence in the self-consistent-field iterations. In these cases, the two-electron contribution to the total energy becomes negative, meaning that the electronic interaction is effectively attractive, and the total energy is dramatically lower than that obtained with exact integrals. In the vast majority of our test cases, however, the indefiniteness does not interfere with convergence. The total energy accuracy is comparable to that of the standard Coulomb-metric RI method. The speed-up compared with conventional algorithms is similar to the RI method for Coulomb contributions; exchange contributions are accelerated by a factor of up to eight with a triple-zeta quality basis set. A positive semidefinite integral matrix is recovered within PARI by introducing local auxiliary basis functions spanning the full AO product space, as may be achieved by using Cholesky-decomposition techniques. Local completion, however, slows down the algorithm to a level comparable with or below conventional calculations.

• Kristensen, Kasper; Høyvik, Ida-Marie; Jansik, Branislav; Jørgensen, Poul; Kjærgaard, Thomas & Reine, Simen Sommerfelt [Vis alle 7 forfattere av denne artikkelen] (2012). MP2 energy and density for large molecular systems with internal error control using the Divide-Expand-Consolidate scheme. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 14(45), s. 15706–15714. doi: 10.1039/c2cp41958k. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt; Helgaker, Trygve & Lindh, Roland (2012). Multi-electron integrals. Wiley Interdisciplinary Reviews. Computational Molecular Science. ISSN 1759-0876. 2(2), s. 290–303. doi: 10.1002/wcms.78. Fulltekst i vitenarkiv
• 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), s. 9492–9499. doi: 10.1039/c2cp40965h. Fulltekst i vitenarkiv
• Kristensen, Kasper; Jørgensen, Poul; Jansik, Branislav; Kjærgaard, Thomas & Reine, Simen Sommerfelt (2012). Molecular gradient for second-order Moller-Plesset perturbation theory using the divide-expand-consolidate (DEC) scheme. Journal of Chemical Physics. ISSN 0021-9606. 137(11). doi: 10.1063/1.4752432. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt; Krapp, Andreas; Iozzi, Maria Francesca; Bakken, Vebjørn; Helgaker, Trygve & Pawlowski, Filip [Vis alle 7 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv
• 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, s. 5344–5348. doi: 10.1039/b807639a. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt; Tellgren, Erik; Krapp, Andreas; Kjærgaard, Thomas; Helgaker, Trygve & Jansik, Branislav [Vis alle 8 forfattere av denne artikkelen] (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. Fulltekst i vitenarkiv Vis sammendrag

  Density fitting is an important method for speeding up quantum-chemical calculations. Linear-scaling developments in Hartree-Fock and density-functional theories have highlighted the need for linear-scaling density-fitting schemes. In this paper, we present a robust variational density-fitting scheme that allows for solving the fitting equations in local metrics instead of the traditional Coulomb metric, as required for linear scaling. Results of fitting four-center two-electron integrals in the overlap and the attenuated Gaussian damped Coulomb metric are presented, and we conclude that density fitting can be performed in local metrics at little loss of chemical accuracy. We further propose to use this theory in linear-scaling density-fitting developments.

• Coriani, Sonia; Høst, Stinne; Jansik, Branislav; Thøgersen, Lea; Olsen, Jeppe & Jørgensen, Poul [Vis alle 10 forfattere av denne artikkelen] (2007). Linear-scaling implementation of molecular response theory in self-consistent field electronic-structure theory. Journal of Chemical Physics. ISSN 0021-9606. 126. Fulltekst i vitenarkiv
• 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, s. 4771–4779. doi: 10.1039/b705594c. Fulltekst i vitenarkiv
• Salek, Pawel; Høst, Stinne; Thøgersen, Lea; Jørgensen, Poul; Manninen, Pekka & Olsen, Jeppe [Vis alle 12 forfattere av denne artikkelen] (2007). Linear-scaling implementation of molecular electronic self-consistent field theory. Journal of Chemical Physics. ISSN 0021-9606. 126. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Reine, Simen (2024). Active Learning through the Hylleraas Software Platform. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2020). The Dalton Project. Fulltekst i vitenarkiv
• Ringholm, Magnus; Bast, Radovan; Friese, Daniel Henrik; Gao, Bin; Jonsson, Dan Johan & Ruud, Kenneth [Vis alle 10 forfattere av denne artikkelen] (2016). Analytic high-order properties with OpenRSP. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• Helgaker, Trygve & Reine, Simen Sommerfelt (2015). Fremtidens nanomedisiner bygger på kvantekjemi. [Journal]. Apollon. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2007). Towards Linear Scaling DFT. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2007). Towards linear scaling HF and DFT in DALTON. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2007). Density-Fitting for Coulomb and Exchange. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2007). Towards Linear Scaling DFT. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2007). Linear Scaling DFT. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt & Helgaker, Trygve (2006). Linear Scaling Density-Fitted Coulomb Evaluation. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2006). Towards linear scaling HF and DFT in DALTON. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2006). Linear Scaling Density–Fitted Coulomb Evaluation. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt & Helgaker, Trygve (2006). Linear Scaling Density-Fitted Coulomb Evaluation. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt (2004). Quantum Monte Carlo simulations of atoms. Fulltekst i vitenarkiv
• 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. Fulltekst i vitenarkiv
• Reine, Simen Sommerfelt; Helgaker, Trygve & Pawlowski, Filip (2009). Density functional theory for large molecular systems. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Accurate simulations of chemical and biological processes at a molecular level have long been missing for a wide range of molecular systems, but in now possible for many of these systems due to the recent developments of Simen Reine, Trygve Helgaker and co-workers at the University of Oslo. Computer simulations are widely used in chemistry and related fields like biology, pharmacy and medicine. Quantum-chemical methods are the basis of the most accurate simulation techniques. They are of great help in the determination and prediction of molecular properties e.g. molecular structures and give important and detailed insights into chemical reactions - both qualitatively and quantitatively. The predictive power and the range of molecular systems these methods can be applied to is closely related to their accuracy, efficiency and user-friendliness, and therefore the development of new and improved methods increases the impact of quantum chemistry to an even greater extent. Such developments enable treatment of systems previously out of reach, improve the description of the systems accessible by standard methodology, and as a consequence, reduce the need for time demanding and costly experiments. Most quantum chemical calculations are carried out using density functional theory (DFT), as this method constitutes a good compromise between accuracy and performance. Although highly useful, current methodology was limited to molecules consisting of up to a few hundred atoms, and the description of for example proteins has therefore been restricted to a rather crude level. In the thesis "Density functional theory for large molecular systems" new methods have been developed aiming at routine DFT calculations of large systems. Molecular calculations on systems containing 1400 atoms are here reported - and the methods have since been applied to systems containing up to 4000 atoms.

Se alle arbeider i NVA