Quasi-linear buildup of Coulomb integrals via the coupling strength parameter in the non-relativistic electronic Schrodinger equation

TL;DR

This paper investigates how Coulomb integrals depend on the coupling strength parameter in the non-relativistic electronic Schrödinger equation, revealing quasi-linear behavior and extending fundamental theorems to this parameter.

Contribution

It introduces a method to analyze Coulomb integrals via the coupling strength parameter and generalizes key quantum chemistry theorems in this context.

Findings

Vee(a) is quasi-linear in a

Extension of Hohenberg-Kohn theorem to a parameter

Algebraic transfer from simplified to physical solutions

Abstract

The non-relativistic electronic Hamiltonian, Hkin + Hne + aHee, is linear in coupling strength parameter (a), but its eigenvalues (electronic energies) have only quasi-linear dependence on it. Detailed analysis is given on the participation of electron-electron repulsion energy (Vee) in total electronic energy (Etotal electr,k) in addition to the well-known virial theorem and standard algorithm for vee(a=1)=Vee calculated during the standard- and post HF-SCF routines. Using a particular modification in the SCF part of the Gaussian package, we have analyzed the ground state solutions via the parameter a. Technically, with a single line in the SCF algorithm, operator was changed as 1/rij-> a/rij with input a. The most important findings are, 1, vee(a) is quasi-linear function of a, 2, the extension of 1st Hohenberg-Kohn theorem (PSI0(a=1)<=>Hne<=>Y0(a=0)) and its consequences in relation to a. The latter allows an algebraic transfer from the simpler solution of case a=0 (where the single Slater determinant Y0 is the accurate form) to the physical case a=1. Moreover, we have generalized the emblematic Hund rule, virial-, Hohenberg-Kohn- and Koopmans theorems in relation to the coupling strength parameter.