Testing several recent van der Waals density functionals for layered structures

TL;DR

This study evaluates six recent van der Waals density functionals paired with exchange functionals for layered materials, benchmarking their accuracy in predicting lattice constants and interlayer binding energies against experimental and RPA data.

Contribution

It provides a comparative assessment of recent vdW-DF functionals for layered structures, highlighting the most accurate combinations for equilibrium geometries.

Findings

OptB86b and cx13 with original vdW-DF perform well for lattice constants.

B86R with vdW-DF2 yields accurate equilibrium geometries.

Most functionals overestimate interlayer binding energies compared to RPA.

Abstract

Six recently developed exchanged functionals for pairing with different two versions of van der Waals density functionals (vdW-DF) are tested for weakly bonded solids. The test, using 26 layered weakly bonded compounds, benchmarks the lattice constants against experimental data and the interlayer binding energies against reference data from the random-phase approximation (RPA). The investigated functionals tend to give interlayer binding energies higher than the RPA benchmark, and the overall performance for lattice constants is good. The exchange functionals optB86b and cx13 paired with the original vdW-DF and the B86R functional paired with vdW-DF2 are found to give particularly good results for equilibrium geometries.