Browsing Kjemisk institutt by Author "Tellgren, Erik"

Now showing items 1-10 of 10

  • A quantum-mechanical non-Born–Oppenheimer model of a molecule in a strong magnetic field 
    Adamowicz, Ludwik; Stanke, Monika; Tellgren, Erik; Helgaker, Trygve (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2020)
    Interactions of a stationary external magnetic field with the spin and orbital magnetic momenta of a molecule are included in the quantum mechanical model where the Born–Oppenheimer approximation is not assumed. The model ...
  • Benchmarking Density Functional Approximations for Diamagnetic and Paramagnetic Molecules in Nonuniform Magnetic Fields 
    Sen, Sangita; Tellgren, Erik (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)
    In this article, correlated studies on a test set of 36 small molecules are carried out with both wavefunction (HF, MP2, CCSD) and density functional (LDA, KT3, cTPSS, cM06-L) methods. The effect of correlation on exotic ...
  • 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, ...
  • Density-wave-function mapping in degenerate current-density-functional theory 
    Laestadius, Andre; Tellgren, Erik (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Coupled cluster (CC) methods are among the most accurate methods in quantum chemistry. However, the standard CC linear response formulation is not gauge invariant, resulting in errors when modelling properties like optical ...
  • 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 ...
  • 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 of a Regularized Kohn-Sham Iteration in Finite Dimensions 
    Penz, Markus; Laestadius, Andre; Tellgren, Erik; Ruggenthaler, Michael (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    The exact Kohn-Sham iteration of generalized density-functional theory in finite dimensions with a Moreau-Yosida regularized universal Lieb functional and an adaptive damping step is shown to converge to the correct ...
  • A local tensor that unifies kinetic energy density and vorticity in density functional theory 
    Sen, Sangita; Tellgren, Erik (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    We present a kinetic energy tensor that unifies a scalar kinetic energy density commonly used in meta-generalized gradient approximation functionals and the vorticity density that appears in paramagnetic current-density-functional ...
  • Magnetic-Field Density-Functional Theory (BDFT): Lessons from the Adiabatic Connection 
    Reimann, Sarah; Borgoo, Alex; Tellgren, Erik; Teale, Andrew Michael; Helgaker, Trygve (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2017)
    We study the effects of magnetic fields in the context of magnetic field density-functional theory (BDFT), where the energy is a functional of the electron density ρ and the magnetic field B. We show that this approach is ...
  • Non-perturbative calculation of orbital and spin effects in molecules subject to non-uniform magnetic fields 
    Sen, Sangita; Tellgren, Erik (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    External non-uniform magnetic fields acting on molecules induce non-collinear spin densities and spin-symmetry breaking. This necessitates a general two-component Pauli spinor representation. In this paper, we report the ...