Exchange-Correlation Energy Functional Based on the Airy-Gas Reference System

TL;DR

This paper introduces a new GGA density functional called ARPA+ based on the Airy gas system, improving exchange-correlation energy calculations for various systems by incorporating RPA correlation data and short-range corrections.

Contribution

The paper develops a novel beyond-RPA GGA functional using Airy gas RPA correlation energy, enhancing accuracy over local density approximations.

Findings

Improves atomization energy predictions.

Enhances lattice constant calculations.

Maintains good surface exchange-correlation energies.

Abstract

In recent work, generalized gradient approximations (GGA's) have been constructed from the energy density of the Airy gas for exchange but not for correlation. We report the random phase approximation (RPA) conventional correlation energy density of the Airy gas, the simplest edge electron gas, in which the auxiliary noninteracting electrons experience a linear potential. By fitting the Airy-gas RPA exchange-correlation energy density and making an accurate short-range correction to RPA, we propose a simple beyond-RPA GGA density functional ("ARPA+") for the exchange-correlation energy. Our functional, tested for jellium surfaces, atoms, molecules and solids, improves mildly over the local spin density approximation for atomization energies and lattice constants without much worsening the already-good surface exchange-correlation energies.