Time‐dependent density functional theory calculation of van der Waals coefficient of potassium clusters

Abstract

AbstractWe employ all‐electron ab initio time‐dependent density functional theory (DFT)‐based method to calculate the long range dipole–dipole dispersion coefficient (van der Waals coefficient)C6of potassium atom clusters (Kn) containing even number of atoms,nranging from 2 to 20. The dispersion coefficients are obtained via Casimir–Polder relation. The calculations are carried out with the asymptotically correct statistical average of orbital potential and compared with the results obtained using Vosko–Wilk–Nusair representation of exchange‐correlation potential within local density approximation. We report the dispersion coefficients between clusters of sodium and potassium atoms as well. The present results have been compared with the available jellium‐based model and other DFT results in the literature. We also study the relationship between volume of the cluster and theC6for K clusters. It is observed that theC6scales as square of the volume. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009