Asymptotic near nucleus structure of the electron-interaction potential in local effective potential theories

TL;DR

This paper analytically investigates the near-nucleus behavior of the electron-interaction potential in local effective potential theories, revealing that correlation-kinetic effects solely determine the linear asymptotic structure.

Contribution

It proves that near the nucleus, the linear structure of the electron-interaction potential is exclusively due to correlation-kinetic effects, with other correlations contributing quadratically or not at all.

Findings

Correlation-kinetic effects determine the linear near-nucleus potential.

Pauli and Coulomb correlations contribute quadratically, not linearly.

Exchange and correlation potentials also approach the nucleus linearly, driven by correlation-kinetic effects.

Abstract

In local effective potential theories of electronic structure, the electron correlations due to the Pauli exclusion principle, Coulomb repulsion, and correlation-kinetic effects, are all incorporated in the local electron-interaction potential $v_{ee}({\bf r})$. In previous work, it has been shown that for spherically symmetric or sphericalized systems, the asymptotic near nucleus expansion of this potential is $v_{ee}(r) = v_{ee}(0) + \beta r + O(r^2)$, with $v_{ee}(0)$ being finite. By assuming that the Schr\"odinger and local effective potential theory wave functions are analytic near the nucleus of atoms, we prove the following via Quantal density functional theory (Q-DFT): (i) correlations due to the Pauli principle and Coulomb correlations do not contribute to the linear structure; (ii) these Pauli and Coulomb correlations contribute quadratically; (iii) the linear structure is {\em solely} due to correlation-kinetic effects, the contributions of these effects being determined analytically. We also derive by application of adiabatic coupling constant perturbation theory via Q-DFT (iv) the asymptotic near nucleus expansion of the Hohenberg-Kohn-Sham theory exchange $v_x({\bf r})$ and correlation $v_c({\bf r})$ potentials. These functions also approach the nucleus linearly with the linear term of $v_x({\bf r})$ being {\em solely} due to the lowest-order correlation kinetic effects, and the linear term of $v_c({\bf r})$ being due {\em solely} to the higher-order correlation kinetic contributions. The above conclusions are equally valid for systems of arbitrary symmetry, provided spherical averages of the properties are employed.