# Nonlocal van der Waals functionals for solids: Choosing an appropriate one

## TL;DR

This paper evaluates various nonlocal van der Waals functionals for solids, finding rev-vdW-DF2 to be highly accurate for both weakly and strongly bound systems, guiding better functional choice.

## Contribution

It provides a comprehensive assessment of NL-vdW functionals for different solid systems, clarifying which functional performs best.

## Key findings

- rev-vdW-DF2 is highly accurate for weakly bound solids
- rev-vdW-DF2 is reliable for strongly bound solids
- Assessment guides functional selection for solid-state calculations

## Abstract

The nonlocal van der Waals (NL-vdW) functionals [Dion et al., Phys. Rev. Lett. 92, 246401 (2004)] are being applied more and more frequently in solid-state physics, since they have shown to be much more reliable than the traditional semilocal functionals for systems where weak interactions play a major role. However, a certain number of NL-vdW functionals have been proposed during the last few years, such that it is not always clear which one should be used. In this work, an assessment of NL-vdW functionals is presented. Our test set consists of weakly bound solids, namely rare gases, layered systems like graphite, and molecular solids, but also strongly bound solids in order to provide a more general conclusion about the accuracy of NL-vdW functionals for extended systems. We found that among the tested functionals, rev-vdW-DF2 [Hamada, Phys. Rev. B 89, 121103(R) (2014)] is very accurate for weakly bound solids, but also quite reliable for strongly bound solids.