Local random phase approximation with projected oscillator orbitals

TL;DR

This paper introduces a local RPA-based method using projected oscillator orbitals to efficiently approximate long-range dispersion energies in molecules, achieving accurate dispersion coefficients with minimal empirical input.

Contribution

It presents a novel local RPA approach with projected oscillator orbitals for calculating dispersion energies based solely on occupied orbitals, improving accuracy and efficiency.

Findings

Reproduces experimental dispersion coefficients within 15% error.

Provides a non-empirical long-range correlation energy expression.

Uses localized orbitals and multipolar expansion for efficient calculations.

Abstract

An approximation to the many-body London dispersion energy in molecular systems is expressed as a functional of the occupied orbitals only. The method is based on the local-RPA theory. The occupied orbitals are localized molecular orbitals and the virtual space is described by projected oscillator orbitals, i.e. functions obtained by multiplying occupied localized orbitals with solid spherical harmonic polynomials having their origin at the orbital centroids. Since we are interested in the long-range part of the correlation energy, responsible for dispersion forces, the electron repulsion is approximated by its multipolar expansion. This procedure leads to a fully non-empirical long-range correlation energy expression. Molecular dispersion coefficients calculated from determinant wave functions obtained by a range-separated hybrid method reproduce experimental values with less than 15% error.