• Adaptive order polynomial algorithm in a multi-wavelet representation scheme 

      Durdek, Antoine Pacifique Romain; Jensen, Stig Rune; Juselius, Jonas; Wind, Peter; Flå, Tor; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • Cavity-Free Continuum Solvation: Implementation and Parametrization in a Multiwavelet Framework 

      Gerez Sazo, Gabriel Adolfo; Remigio Eikås, Roberto Di; Jensen, Stig Rune; Bjørgve, Magnar; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-18)
      We present a multiwavelet-based implementation of a quantum/classical polarizable continuum model. The solvent model uses a diffuse solute–solvent boundary and a position-dependent permittivity, lifting the sharp-boundary assumption underlying many existing continuum solvation models. We are able to include both surface and volume polarization effects in the quantum/classical coupling, with guaranteed ...
    • The Elephant in the Room of Density Functional Theory Calculations 

      Jensen, Stig Rune; Saha, Santanu; Flores-Livas, Jose A; Huhn, William; Blum, Volker; Goedecker, Stefan; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-14)
      Using multiwavelets, we have obtained total energies and corresponding atomization energies for the GGA-PBE and hybrid-PBE0 density functionals for a test set of 211 molecules with an unprecedented and guaranteed μHartree accuracy. These quasi-exact references allow us to quantify the accuracy of standard all-electron basis sets that are believed to be highly accurate for molecules, such as Gaussian-type ...
    • Full Breit Hamiltonian in the Multiwavelets Framework 

      Tantardini, Christian; Remigio, Roberto Di; Bjørgve, Magnar; Jensen, Stig Rune; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-01-01)
      New techniques in core–electron spectroscopy are necessary to resolve the structures of oxides of f-elements and other strongly correlated materials that are present only as powders and not as single crystals. Thus, accurate quantum chemical methods must be developed to calculate core spectroscopic properties in such materials. In this contribution, we present an important development in this ...
    • Linear scaling Coulomb interaction in the multiwavelet basis, a parallel implementation 

      Jensen, Stig Rune; Juselius, Jonas; Durdek, Antoine Pacifique Romain; Flå, Tor; Wind, Peter; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-08-27)
      We present a parallel and linear scaling implementation of the calculation of the electrostatic potential arising from an arbitrary charge distribution. Our approach is making use of the multi-resolution basis of multiwavelets. The potential is obtained as the direct solution of the Poisson equation in its Green’s function integral form. In the multiwavelet basis, the formally non local ...
    • Magnetic properties with multiwavelets and DFT: The complete basis set limit achieved 

      Jensen, Stig Rune; Flå, Tor; Jonsson, Dan Johan; Monstad, Rune Sørland; Ruud, Kenneth; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-11)
      Multiwavelets are emerging as an attractive alternative to traditional basis sets such as Gaussian-type orbitals and plane waves. One of their distinctive properties is the ability to reach the basis set limit (often a chimera for traditional approaches) reliably and consistently by fixing the desired precision ε. We present our multiwavelet implementation of the linear response formalism, applied ...
    • Multiwavelets applied to metal–ligand interactions: Energies free from basis set errors 

      Brakestad, Anders; Wind, Peter; Jensen, Stig Rune; Frediani, Luca; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-02)
      Transition metal-catalyzed reactions invariably include steps where ligands associate or dissociate. In order to obtain reliable energies for such reactions, sufficiently large basis sets need to be employed. In this paper, we have used high-precision multiwavelet calculations to compute the metal–ligand association energies for 27 transition metal complexes with common ligands, such as H2, CO, ...
    • On derivatives of smooth functions represented in multiwavelet bases 

      Anderson, Joel; Harrison, Robert J.; Sekino, Hideo; Sundahl, Bryan; Beylkin, Gregory; Fann, George I.; Jensen, Stig Rune; Sagert, Irina (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-24)
      We construct high-order derivative operators for smooth functions represented via discontinuous multiwavelet bases. The need for such operators arises in order to avoid artifacts when computing functionals involving high-order derivatives of solutions of integral equations. Previously high-order derivatives had to be formed by repeated application of a first-derivative operator that, while uniquely ...
    • Scalar Relativistic Effects with Multiwavelets: Implementation and Benchmark 

      Brakestad, Anders; Jensen, Stig Rune; Tantardini, Christian; Pitteloud, Quentin Gregoire; Wind, Peter Ariaan; Užulis, Jānis; Gulans, Andris; Hopmann, Kathrin Helen; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-01-05)
      The importance of relativistic effects in quantum chemistry is widely recognized, not only for heavier elements but throughout the periodic table. At the same time, relativistic effects are strongest in the nuclear region, where the description of electrons through a linear combination of atomic orbitals becomes more challenging. Furthermore, the choice of basis sets for heavier elements is ...
    • Static polarizabilities at the basis set limit: A benchmark of 124 species 

      Brakestad, Anders; Jensen, Stig Rune; Wind, Peter; D'Alessandro, Marco; Genovese, Luigi; Hopmann, Kathrin Helen; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-16)
      Benchmarking molecular properties with Gaussian-type orbital (GTO) basis sets can be challenging, because one has to assume that the computed property is at the complete basis set (CBS) limit, without a robust measure of the error. Multiwavelet (MW) bases can be systematically improved with a controllable error, which eliminates the need for such assumptions. In this work, we have used MWs within ...