Browsing Kjemisk institutt by Author "Kvaal, Simen"

Now showing items 1-20 of 22

  • A state-specific multireference coupled-cluster method based on the bivariational principle 
    Bodenstein, Tilmann; Kvaal, Simen (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2020)
    A state-specific multireference coupled-cluster (MRCC) method based on Arponen’s bivariational principle is presented, the bivar-MRCC method. The method is based on single-reference theory and therefore has a relatively ...
  • Accelerated coupled cluster calculations with Procrustes orbital interpolation 
    Schrader, Simon Elias; Kvaal, Simen (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2023)
    The coupled cluster method is considered a gold standard in quantum chemistry, reliably giving energies that are exact within chemical accuracy (1.6 mhartree). However, even in the coupled cluster single-double (CCSD) ...
  • Adiabatic extraction of nonlinear optical properties from real-time time-dependent electronic-structure theory 
    Ofstad, Benedicte Sverdrup; Kristiansen, Håkon Emil; Aurbakken, Einar; Schøyen, Øyvind Sigmundson; Kvaal, Simen; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
    Real-time simulations of laser-driven electron dynamics contain information about molecular optical properties through all orders in response theory. These properties can be extracted by assuming convergence of the power ...
  • Analysis of the Extended Coupled-Cluster Method in Quantum Chemistry 
    Laestadius, Andre; Kvaal, Simen (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    The mathematical foundation of the so-called extended coupled-cluster method for the solution of the many-fermion Schrödinger equation is here developed. We prove an existence and uniqueness result, both in the full ...
  • Analysis of the Tailored Coupled-Cluster Method in Quantum Chemistry 
    Faulstich, Fabian Maximilian; Laestadius, Andre; Legeza, Örs; Schneider, Reinhold; Kvaal, Simen (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    n quantum chemistry, one of the most important challenges is the static correlation problem when solving the electronic Schrödinger equation for molecules in the Born--Oppenheimer approximation. In this article, we analyze ...
  • Choice of basic variables in current-density-functional theory 
    Tellgren, Erik; Kvaal, Simen; Sagvolden, Espen; Ekström, Ulf Egil; Teale, Andrew Michael; Helgaker, Trygve (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
    The selection of basic variables in current-density-functional theory and formal properties of the resulting formulations are critically examined. Focus is placed on the extent to which the Hohenberg-Kohn theorem, ...
  • Computing all Pairs (λ,μ) Such That λ is a Double Eigenvalue of Α + μΒ 
    Jarlebring, Elias; Kvaal, Simen; Michiels, Wim (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2011)
    Double eigenvalues are not generic for matrices without any particular structure. A matrix depending linearly on a scalar parameter, Α + μΒ, will, however, generically have double eigenvalues for some values of the parameter ...
  • DFT exchange: sharing perspectives on the workhorse of quantum chemistry and materials science 
    Teale, Andrew Michael; Helgaker, Trygve; Savin, Andreas; Adamo, Carlo; Aradi, Balint; Arbuznikov, Alexei V.; Ayers, Paul W.; Baerends, Evert Jan; Barone, Vincenzo; Calaminici, Patrizia; Cances, Eric; Carter, Emily A.; Chattaraj, Pratim Kumar; Chermette, Henry; Ciofini, Ilaria; Crawford, T. Daniel; de Proft, Frank; Dobson, John F.; Draxl, Claudia; Frauenheim, Thomas; Fromager, Emmanuel; Fuentealba, Patricio; Gagliardi, Laura; Galli, Giulia; Gao, Jaili; Geerlings, Paul; Gidopoulos, Nikitas I.; Gill, Peter M. W.; Gori-Giorgi, Paola; Görling, Andreas; Gould, Tim; Grimme, Stefan; Gritsenko, Oleg; Jensen, Hans Jørgen Aagaard; Johnson, Erin R.; Jones, Robert O.; Kaupp, Martin; Köster, Andreas M.; Kronik, Leeor; Krylov, Anna I.; Kvaal, Simen; Laestadius, Andre; Levy, Mel; Lewin, Mathieu; Liu, Shubin; Loos, Pierre-Francois; Maitra, Neepa T.; Neese, Frank; Perdew, John P.; Pernal, Katarzyna; Pernot, Pascal; Piecuch, Piotr; Rebolini, Elisa; Reining, Lucia; Romaniello, Pina; Ruzsinszky, Adrienn; Salahub, Dennis R.; Scheffler, Matthias; Schwerdtfeger, Peter; Staroverov, Viktor N.; Sun, Jianwei; Tellgren, Erik Ingemar; Tozer, David J.; Trickey, Samuel B.; Ullrich, Carsten A.; Vela, Alberto; Vignale, Giovanni; Wesolowski, Tomasz A.; Xu, Xin; Yang, Weitao (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2022)
    In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method ...
  • Fermion N -representability for prescribed density and paramagnetic current density 
    Tellgren, Erik; Kvaal, Simen; Helgaker, Trygve (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    The N-representability problem is the problem of determining whether there exists N-particle states with some prescribed property. Here we report an affirmative solution to the fermion N-representability problem when both ...
  • Gaussians for Electronic and Rovibrational Quantum Dynamics 
    Wozniak, Aleksander P.; Adamowicz, Ludwik; Pedersen, Thomas Bondo; Kvaal, Simen (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2024)
    The assumptions underpinning the adiabatic Born-Oppenheimer (BO) approximation are broken for molecules interacting with attosecond laser pulses, which generate complicated coupled electronic-nuclear wave packets that ...
  • Generalized Kohn-Sham iteration on Banach spaces 
    Laestadius, Andre; Penz, Markus; Tellgren, Erik; Ruggenthaler, Michael; Kvaal, Simen; Helgaker, Trygve (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2018)
    A detailed account of the Kohn–Sham (KS) algorithm from quantum chemistry, formulated rigorously in the very general setting of convex analysis on Banach spaces, is given here. Starting from a Levy–Lieb-type functional, ...
  • Guaranteed convergence for a class of coupled-cluster methods based on Arponen's extended theory 
    Kvaal, Simen; Laestadius, Andre; Bodenstein, Tilmann (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    A wide class of coupled-cluster methods is introduced, based on Arponen's extended coupled-cluster theory. This class of methods is formulated in terms of a coordinate transformation of the cluster operators. The mathematical ...
  • Interpretation of Coupled-Cluster Many-Electron Dynamics in Terms of Stationary States 
    Pedersen, Thomas Bondo; Kristiansen, Håkon Emil; Bodenstein, Tilmann; Kvaal, Simen; Schøyen, Øyvind Sigmundson (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    We demonstrate theoretically and numerically that laser-driven many-electron dynamics, as described by bivariational time-dependent coupled-cluster theory, may be analyzed in terms of stationary-state populations. Projectors ...
  • Laser-induced dynamic alignment of the HD molecule without the Born-Oppenheimer approximation 
    Adamowicz, Ludwik; Kvaal, Simen; Lasser, Caroline; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2022)
    Laser-induced molecular alignment is well understood within the framework of the Born-Oppenheimer (BO) approximation. Without the BO approximation, however, the concept of molecular structure is lost, making alignment hard ...
  • Linear and Nonlinear Optical Properties from TDOMP2 Theory 
    Kristiansen, Håkon Emil; Ofstad, Benedicte Sverdrup; Hauge, Eirill Strand; Aurbakken, Einar; Schøyen, Øyvind Sigmundson; Kvaal, Simen; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2022)
    We present a derivation of real-time (RT) time-dependent orbital-optimized Møller–Plesset (TDOMP2) theory and its biorthogonal companion, time-dependent non-orthogonal OMP2 theory, starting from the time-dependent bivariational ...
  • Lower Semicontinuity of the Universal Functional in Paramagnetic Current-Density Functional Theory 
    Kvaal, Simen; Laestadius, Andre; Tellgren, Erik Ingemar; Helgaker, Trygve (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    A cornerstone of current–density functional theory (CDFT) in its paramagnetic formulation is proven. After a brief outline of the mathematical structure of CDFT, the lower semicontinuity and expectation-valuedness of the ...
  • Magnetic optical rotation from real-time simulations in finite magnetic fields 
    Ofstad, Benedicte; Wibowo-Teale, Meilani; Kristiansen, Håkon Emil; Aurbakken, Einar; Kitsaras, Marios-Petros; Schøyen, Øyvind Sigmundson; Hauge, Eirill Strand; Irons, Tom J. P.; Kvaal, Simen; Stopkowicz, Stella; Wibowo-Teale, Andrew M.; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2023)
    We present a numerical approach to magnetic optical rotation based on real-time time-dependent electronic-structure theory. Not relying on perturbation expansions in the magnetic-field strength, the formulation allows us ...
  • Numerical stability of time-dependent coupled-cluster methods for many-electron dynamics in intense laser pulses 
    Kristiansen, Håkon Emil; Schøyen, Øyvind Sigmundson; Kvaal, Simen; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2020)
    We investigate the numerical stability of time-dependent coupled-cluster theory for many-electron dynamics in intense laser pulses, comparing two coupled-cluster formulations with full configuration interaction theory. Our ...
  • Symplectic integration and physical interpretation of time-dependent coupled-cluster theory 
    Pedersen, Thomas Bondo; Kvaal, Simen (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2019)
    The formulation of the time-dependent Schrödinger equation in terms of coupled-cluster theory is outlined, with emphasis on the bivariational framework and its classical Hamiltonian structure. An indefinite inner product ...
  • The S-diagnostic - an a posteriori error assessment for single-reference coupled-cluster methods 
    Faulstich, Fabian M.; Kristiansen, Håkon Emil; Csirik, Mihaly Andras; Kvaal, Simen; Pedersen, Thomas Bondo; Laestadius, Andre (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2023)
    We propose a novel a posteriori error assessment for the single-reference coupled-cluster (SRCC) method called the S-diagnostic. We provide a derivation of the S-diagnostic that is rooted in the mathematical analysis of ...