Accurate Molecular Van Der Waals Interactions from Ground-State Electron Density and Free-Atom Reference Data

TLDR

We present a parameter‑free method for accurately determining long‑range van der Waals interactions from mean‑field electronic structure calculations. The method sums interatomic C6 coefficients derived from a molecule’s electron density and free‑atom reference data, and it also analyzes van der Waals radii and the damping function in the C6R(–6) correction for density‑functional theory. The mean absolute error in the C6 coefficients is 5.5 % versus experimental values for 1,225 pairs, independent of the exchange‑correlation functional, and the effective atomic C6 coefficients vary strongly with the bonding environment.

Abstract

We present a parameter-free method for an accurate determination of long-range van der Waals interactions from mean-field electronic structure calculations. Our method relies on the summation of interatomic C6 coefficients, derived from the electron density of a molecule or solid and accurate reference data for the free atoms. The mean absolute error in the C6 coefficients is 5.5% when compared to accurate experimental values for 1225 intermolecular pairs, irrespective of the employed exchange-correlation functional. We show that the effective atomic C6 coefficients depend strongly on the bonding environment of an atom in a molecule. Finally, we analyze the van der Waals radii and the damping function in the C6R(-6) correction method for density-functional theory calculations.