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koopmans: an open-source package for accurately and efficiently predicting spectral properties with Koopmans functionals

Edward Linscott1*, Nicola Colonna2,3, Riccardo De Gennaro1, Ngoc Linh Nguyen4,5, Giovanni Borghi1,6, Andrea Ferretti7, Ismaila Dabo8, Nicola Marzari1,3*

1 Theory and Simulation of Materials (THEOS), École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

2 Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland

3 National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

4 Faculty of Materials Science and Engineering, Phenikaa University, Hanoi 12116, Vietnam

5 Phenikaa Research and Technology Institute (PRATI), A&A Green Phoenix Group JSC, No. 167 Hoang Ngan, Trung Hoa, Cau Giay, Hanoi 11313, Vietnam

6 Now at Liceo Manfredo Fanti, 41012 Carpi, Italy

7 Centro S3, CNR--Istituto Nanoscienze, 41125 Modena, Italy

8 Department of Materials Science and Engineering, Materials Research Institute, and Institutes of Energy and the Environment, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

* Corresponding authors emails: edward.linscott@epfl.ch, nicola.marzari@epfl.ch
DOI10.24435/materialscloud:9w-sp [version v1]

Publication date: Feb 17, 2023

How to cite this record

Edward Linscott, Nicola Colonna, Riccardo De Gennaro, Ngoc Linh Nguyen, Giovanni Borghi, Andrea Ferretti, Ismaila Dabo, Nicola Marzari, koopmans: an open-source package for accurately and efficiently predicting spectral properties with Koopmans functionals, Materials Cloud Archive 2023.27 (2023), doi: 10.24435/materialscloud:9w-sp.


Over the past decade we have developed Koopmans functionals, a computationally efficient approach for predicting spectral properties with an orbital-density-dependent functional formulation. These functionals address two fundamental issues with density functional theory (DFT). First, while Kohn-Sham eigenvalues can loosely mirror experimental quasiparticle energies, they are not meant to reproduce excitation energies and there is formally no connection between the two (except for the HOMO for the exact functional). Second, (semi-)local DFT deviates from the expected piecewise linear behavior of the energy as a function of the total number of electrons. This can make eigenvalues an even poorer proxy for quasiparticle energies and, together with the absence of the exchange-correlation derivative discontinuity, contributes to DFT's underestimation of band gaps. By enforcing a generalized piecewise linearity condition to the entire electronic manifold, Koopmans functionals yield molecular orbital energies and solids-state band structures with comparable accuracy to many-body perturbation theory but at greatly reduced computational cost and preserving a functional formulation. This paper introduces "koopmans", an open-source package that contains all of the code and workflows needed to perform Koopmans functional calculations without requiring expert knowledge. The theory and algorithms behind Koopmans functionals are summarized, and it is shown how one can easily use the koopmans package to obtain reliable spectral properties of molecules and materials. This archive contains files that accompany the article of the same name.

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File name Size Description
42.6 MiB Input and output files for Koopmans functional calculations on ozone, bulk silicon, and bulk zinc oxide
993 Bytes Extended description of the archive contents


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orbital-density dependent functionals Koopmans spectral functionals electronic structure electronic bands charged excitations SNSF MARVEL

Version history:

2023.27 (version v1) [This version] Feb 17, 2023 DOI10.24435/materialscloud:9w-sp