Exact partition potential for model systems of interacting electrons in 1-D

TL;DR

This paper computes the exact partition potential for 1-D interacting electron systems modeling diatomic molecules, revealing features critical for density-embedding methods and the role of kinetic and exchange-correlation energies.

Contribution

It provides the numerically exact partition potential for 1-D electron models, analyzing its features at different fragment occupations and their implications for density functional approximations.

Findings

Sharp features in the kinetic contribution at integer occupations

Features of the partition potential align with molecular Kohn-Sham potential

Non-integer occupations are governed by fragment Kohn-Sham gaps

Abstract

We find the numerically exact partition potential for 1-D systems of interacting electrons designed to model diatomic molecules. At integer fragment occupations, the kinetic contribution to the partition potential develops sharp features in the internuclear region that nearly cancel corresponding features of exchange-correlation. They occur at locations that coincide with those of well-known features of the underlying molecular Kohn-Sham potential. For non-integer fragment occupations, we demonstrate that the fragment Kohn-Sham gaps determine the kinetic part of the partition potential. Our results highlight the importance of non-additive noninteracting kinetic and exchange-correlation energy approximations in density-embedding methods at large internuclear separations and the importance of non-additive noninteracting kinetic energy approximations at all separations.