Browsing Kjemisk institutt by Author "Pedersen, Thomas Bondo"

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  • A Quantum Definition of Molecular Structure 
    Lang, Lucas; Cezar, Henrique Musseli; Adamowicz, Ludwik; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
    Molecular structure, a key concept of chemistry, has remained elusive from the perspective of all-particle quantum mechanics despite many efforts. Viewing molecular structure as a manifestation of strong statistical ...
  • 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 ...
  • Cost-Efficient High-Resolution Linear Absorption Spectra Through Extrapolating the Dipole Moment from Real-Time Time-Dependent Electronic-Structure Theory 
    Hauge, Eirill Strand; Kristiansen, Håkon Emil; Konecny, Lukas; Kadek, Marius; Repisky, Michal; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
    We present a novel function fitting method for approximating the propagation of the time-dependent electric dipole moment from real-time electronic structure calculations. Real-time calculations of the electronic absorption ...
  • Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems 
    Olsen, Jógvan Magnus Haugaard; Reine, Simen Sommerfelt; Vahtras, Olav; Kjellgren, Erik; Reinholdt, Peter; Dundas, Karen O.H; Li, Xin; Cukras, Janusz; Ringholm, Magnus; Hedegård, Erik Donovan; Di Remigio, Roberto; List, Nanna H.; Faber, Rasmus; Tenorio, Bruno Nunes Cabral; Bast, Radovan; Pedersen, Thomas Bondo; Rinkevicius, Zilvinas; Sauer, Stephan P. A.; Mikkelsen, Kurt V.; Kongsted, Jacob; Coriani, Sonia; Ruud, Kenneth; Helgaker, Trygve; Jensen, Hans Jørgen Aa.; Norman, Patrick (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    The Dalton Project 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 ...
  • Deep learning metal complex properties with natural quantum graphs 
    Kneiding, Hannes; Lukin, Ruslan; Lang, Lucas; Reine, Simen; Pedersen, Thomas Bondo; De Bin, Riccardo; Balcells, David (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)
    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 ...
  • Divide-Expand-Consolidate Second-Order Møller-Plesset Theory with Periodic Boundary Conditions 
    Rebolini, Elisa; Baardsen, Gustav; Hansen, Audun Skau; Leikanger, Karl Roald; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2018)
    We present a generalization of the divide–expand–consolidate (DEC) framework for local coupled-cluster calculations to periodic systems and test it at the second-order Møller–Plesset (MP2) level of theory. For simple model ...
  • 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 ...
  • Inner projection techniques for the low-cost handling of two-electron integrals in quantum chemistry 
    Aquilante, Francesco; Delcey, Mickaël G.; Pedersen, Thomas Bondo; Fdez Galvan, Ignacio; Lindh, Roland (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
    The density-fitting technique for approximating electron-repulsion integrals relies on the quality of auxiliary basis sets. These are commonly obtained through data fitting, an approach that presents some shortcomings. On ...
  • 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 ...
  • 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 ...
  • Modern quantum chemistry with [Open]Molcas 
    Aquilante, Francesco; Autschbach, Jochen; Baiardi, Alberto; Battaglia, Stefano; Borin, Veniamin A.; Chibotaru, Liviu F.; Conti, Irene; de Vico, Luca; Delcey, Michael; Galván, Ignacio Fdez.; Ferré, Nicolas; Freitag, Leon; Garavelli, Marco; Gong, Xuejun; Knecht, Stefan; Larsson, Ernst D.; Lindh, Roland; Lundberg, Marcus; Malmqvist, Per-Åke; Nenov, Artur; Norell, Jesper; Odelius, Michael; Olivucci, Massimo; Pedersen, Thomas Bondo; Pedraza-Gonzalez, Laura; Phung, Quan M.; Pierloot, Kristine; Reiher, Markus; Schapiro, Igor; Segarra-Martí, Javier; Segatta, Francesco; Seijo, Luis; Sen, Saumik; Sergentu, Dumitru-Claudiu; Stein, Christopher J.; Ungur, Liviu; Vacher, Morgane; Valentini, Alessio; Veryazov, Valera (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    MOLCAS/OpenMolcas is an ab initio electronic structure program providing a large set of computational methods from Hartree–Fock and density functional theory to various implementations of multiconfigurational theory. This ...
  • 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 ...
  • On Resolution-of-the-Identity Electron Repulsion Integral Approximations and Variational Stability 
    Wirz, Lukas Nico; Reine, Simen Sommerfelt; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
    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. ...
  • Orbital entanglement and CASSCF analysis of the Ru-NO bond in a Ruthenium nitrosyl complex 
    Freitag, Leon; Knecht, Stefan; Keller, Sebastian F.; Delcey, Mickaël G.; Aquilante, Francesco; Pedersen, Thomas Bondo; Lindh, Roland; Reiher, Markus; González, Leticia (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    Complete active space self-consistent field (CASSCF) wavefunctions and an orbital entanglement analysis obtained from a density-matrix renormalisation group (DMRG) calculation are used to understand the electronic structure, ...
  • Representation of the virtual space in extended systems – a correlation energy convergence study 
    Hansen, Audun Skau; Baardsen, Gustav; Rebolini, Elisa; Maschio, Lorenzo; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    We present an investigation of the convergence behaviour of the local second-order Møller-Plesset perturbation theory (MP2) correlation energy toward the canonical result for three insulating crystals with either projected ...
  • Smooth potential-energy surfaces in fragmentation-based local correlation methods for periodic systems 
    Hansen, Audun Skau; Aurbakken, Einar; Pedersen, Thomas Bondo (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    Local approximations facilitate the application of post-Hartree–Fock methods in the condensed phase, but simultaneously introduce errors leading to discontinuous potential-energy surfaces. In this work, we explore how these ...
  • 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 ...