An exchange functional that tests the robustness of the plasmon description of the van der Waals density functional

TL;DR

This paper introduces a new exchange functional, LV-PW86r, based on the plasmon description of the van der Waals density functional, and demonstrates its effectiveness in accurately predicting molecular and solid-state properties.

Contribution

The paper develops and tests a new exchange functional, LV-PW86r, that extends the plasmon description of vdW-DF1 to improve accuracy in diverse systems.

Findings

Accurately predicts molecular dimer binding energies.

Provides precise lattice constants for layered materials.

Shows vdW-DF1's good plasmon description in low-to-moderate s-regime.

Abstract

Is the plasmon description within the non-local correlation of the van der Waals density functional by Dion and coworkers (vdW-DF1) robust enough to describe all exchange-correlation components? To address this question, we design an exchange functional, termed LV-PW86r based on this plasmon description as well as recent analysis on exchange in the large $s$-regime. In the regime with reduced gradients $s=|\nabla n|/2n k_{\rm F}(n)$ smaller than $\approx 2.5$, dominating the non-local correlation part of the binding energy, the enhancement factor $F_x(s)$ closely resembles the Langreth-Vosko screened exchange. In the $s$-regime beyond, dominated by exchange, $F_x(s)$ passes smoothly over to the revised Perdew-Wang-86 form. Our tests indicate that vdW-DF1(LV-PW86r) produces accurate separations and binding energies of the S22 data set of molecular dimers as well as accurate lattice constants of layered materials and tightly-bound solids. These results suggest that vdW-DF1 has a good plasmon description in the low-to-moderate $s$-regime.