Van der Waals Coefficients of Atoms and Molecules from a Simple Approximation for the Polarizability

TL;DR

This paper introduces a simple, efficient method within density functional theory to approximate van der Waals coefficients by calculating imaginary-frequency polarizabilities using the Thomas-Fermi-von Weizs"acker approximation, showing promising results for atoms and molecules.

Contribution

It presents a novel, computationally efficient scheme for estimating van der Waals coefficients using an approximate polarizability within DFT, based on the TFvW approximation.

Findings

Accurately estimates van der Waals coefficients for ions and molecules

Shows good agreement with first-principles calculations

Potential to improve functional development for long-range interactions

Abstract

A simple and computationally efficient scheme to calculate approximate imaginary-frequency dependent polarizability, hence asymptotic van der Waals coefficient, within density functional theory is proposed. The dynamical dipolar polarizabilities of atoms and molecules are calculated starting from the Thomas-Fermi-von Weizs\"acker (TFvW) approximation for the independent-electron kinetic energy functional. The van der Waals coefficients for a number of closed-shell ions and a few molecules are hence calculated and compared with available values obtained by fully first-principles calculations. The success in these test cases shows the potential of the proposed TFvW approximate response function in capturing the essence of long range correlations and may give useful information for constructing a functional which naturally includes van der Waals interactions.