Time-Dependent Density Functional Theory Calculation of Van der Waals Coefficient of Metal Clusters

We discuss two methods within the realm of time‐dependent density functional theory to calculate frequency dependent polarizabilty of many‐electron systems and use them to obtain van der Waals coefficient C6 between two such systems. One method is based on time dependent Kohn‐Sham formalism and the other one is hydrodynamic approach based in terms of particle‐ and current‐density. We apply these methods to calculate C6 of inert gas atoms and alkali metal clusters within the jellium model and at the ab initio level as well by taking discrete ionic positions into account. The accuracy of the jellium model results are assessed against more accurate ab initio data.