Van der Waals Density Functional for Layered Structures

TLDR

Sparse systems require accounting for both strong local bonds and weak nonlocal van der Waals forces. The authors use a fully nonlocal density‑functional theory functional to compute bond lengths, binding energies, and compressibilities of graphite, boron nitride, and molybdenum sulfide. The fully nonlocal DFT accurately predicts properties of these sparse layered materials, whereas the generalized‑gradient approximation fails. The functional is based on the fully nonlocal approach presented in Phys.

Abstract

To understand sparse systems, we must account for both strong local atom bonds and weak nonlocal van der Waals forces between atoms separated by empty space. A fully nonlocal functional form [Phys. Rev. B 62, 6997 (2000)]] of density-functional theory (DFT) is applied here to the layered systems graphite, boron nitride, and molybdenum sulfide to compute bond lengths, binding energies, and compressibilities. These key examples show that the DFT with the generalized-gradient approximation does not apply for calculating properties of sparse matter, while use of the fully nonlocal version appears to be one way to proceed.