A full implementation of the response iteration scheme for density functional calculations.

We describe the implementation of the response algorithm for solving the Kohn-Sham equations and equations of similar structure that appear frequently in calculations of the structure of inhomogeneous many-body systems. The algorithm solves directly for the (spin) density. We have implemented the method for arbitrary geometries in a way that does not need the explicit calculation of unoccupied states.

Van der Waals interactions: accuracy of pair potential approximations.

Van der Waals interactions between single atoms and solids are discussed for the regime of large separation. A commonly employed approximation is to evaluate this interaction as a sum of two-body interactions between the adatom and the constituent atoms of the solid. The resulting potentials are here compared with known results in various geometries.