Nuclear cusps and singularities in the nonadditive kinetic pote…

The nonadditive kinetic potential is a key quantity in density-functional theory (DFT) embedding methods, such as frozen density embedding theory and partition DFT. is a bifunctional of electron densities and . It can be evaluated using approximate kinetic-energy functionals, but accurate approximations are challenging. The behavior of in the vicinity of the nuclei has long been questioned, and singularities were seen in some approximate calculations. In this article, the existence of singularities in is analyzed analytically for various choices of and , using the nuclear cusp conditions for the density and Kohn-Sham potential. It is shown that no singularities arise from smoothly partitioned ground-state Kohn-Sham densities. We confirm this result by numerical calculations on diatomic test systems HeHe, , and , using analytical inversion to obtain a numerically exact for the local density approximation. We examine features of which can be used for development and testing of approximations to and kinetic-energy functionals.

Received 1 July 2022

Accepted 29 September 2022

DOI:https://doi.org/10.1103/PhysRevA.106.042812

©2022 American Physical Society

Research Areas

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

David A. Strubbe1,¶

1Department of Physics, University of California, Merced, Merced, California 95348, USA

2Département de Chimie Physique 30, Université de Genève, Quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland

3Queensland Micro and Nanotechnology Centre, Griffith University, Nathan, Queensland 4111, Australia

4Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovoth 76100, Israel

*mbanafsheh@ucmerced.edu

†tomasz.wesolowski@unige.ch

‡t.gould@griffith.edu.au

§leeor.kronik@weizmann.ac.il

¶dstrubbe@ucmerced.edu