Symmetrized non-decomposable approximations of the non-additive kinetic energy functional

Elias Polak; Tanguy Englert; Martin J Gander; Tomasz A Wesolowski

doi:10.1063/5.0143602

Symmetrized non-decomposable approximations of the non-additive kinetic energy functional

J Chem Phys. 2023 May 7;158(17):174107. doi: 10.1063/5.0143602.

Authors

Elias Polak^{1

2}, Tanguy Englert¹, Martin J Gander², Tomasz A Wesolowski¹

Affiliations

¹ Department of Physical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Genève 4, Switzerland.
² Section of Mathematics, University of Geneva, Rue du Conseil-Général 7-9, CP 64, CH-1211 Genève 4, Switzerland.

PMID: 37129139
DOI: 10.1063/5.0143602

Abstract

In subsystem density functional theory (DFT), the bottom-up strategy to approximate the multivariable functional of the non-additive kinetic energy (NAKE) makes it possible to impose exact properties on the corresponding NAKE potential (NAKEP). Such a construction might lead to a non-symmetric and non-homogeneous functional, which excludes the use of such approximations for the evaluation of the total energy. We propose a general formalism to construct a symmetric version based on a perturbation theory approach of the energy expression for the asymmetric part. This strategy is then applied to construct a symmetrized NAKE corresponding to the NAKEP developed recently [Polak et al., J. Chem. Phys. 156, 044103 (2022)], making it possible to evaluate consistently the energy. These functionals were used to evaluate the interaction energy in several model intermolecular complexes using the formal framework of subsystem DFT. The new symmetrized energy expression shows a superior qualitative performance over common decomposable models.