Long-range configuration interaction with an ab initio short-range correction and an asymptotic lower bound

TL;DR

This paper introduces a rigorous, perturbation theory-based method for short-range corrections in long-range configuration interaction calculations, achieving high accuracy without fitting to reference data.

Contribution

It develops a new ab initio short-range correction approach for long-range configuration interaction, providing lower bounds and improved energies over existing density functional methods.

Findings

Method yields energies within chemical accuracy.

Provides rigorous lower bounds for energy calculations.

Outperforms some density functional approximations.

Abstract

Short-range corrections to long-range selected configuration interaction calculations are derived from perturbation theory considerations and applied to harmonium (with two to six electrons for some low-lying states). No fitting to reference data is used, and the method is applicable to ground and excited states. The formulas derived are rigorous when the physical interaction is approached. In this regime, the second-order expression provides a lower bound to the long-range full configuration interaction energy. A long-range/short-range separation of the interaction between electrons at a distance of the order of one atomic unit provides total energies within chemical accuracy, and, for the systems studied, provide better results than short-range density functional approximations.