  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.

Materials Science;Chemical Physics