Van der Waals density functional: an appropriate exchange functional

TL;DR

This paper introduces a new exchange functional compatible with vdW-DF that significantly improves intermolecular distance predictions and interaction energies, enhancing the applicability of density functional theory to large dispersion-bound complexes.

Contribution

A novel three-parameter exchange functional compatible with vdW-DF, improving accuracy of intermolecular distances and energies in dispersion-bound systems.

Findings

Enhanced accuracy of intermolecular separation distances.

Improved vdW-DF interaction energy predictions.

Potential for broader application in large complexes.

Abstract

In this paper, an exchange functional which is compatible with the non-local Rutgers-Chalmers correlation functional (vdW-DF) is presented. This functional, when employed with vdW-DF, demonstrates remarkable improvements on intermolecular separation distances while further improving the accuracy of vdW-DF interaction energies. The key to the success of this three parameter functional is its reduction of short range exchange repulsion through matching to the gradient exchange approximation in the slowly varying/high density limit while recovering the large reduced gradient, s, limit set in the revised PBE exchange functional. This augmented exchange functional could be a solution to long-standing issues of vdW-DF lending to further applicability of density functional theory to the study of relatively large, dispersion bound (van der Waals) complexes.