Static Nonlocal Dielectric Function of Liquid Water

The wave vector dependent longitudinal static dielectric function ε(k) of water is calculated in a broad k range by means of molecular dynamics simulation for a central force model and is compared with ε(k) determined from neutron diffraction data. It exhibits a decrease at small k, two divergence points on the k axis with a range of negative values in between, and the correct physical limit, ε(k→∞)0ex0ex=0ex0ex1. The response function, 1-1/ε(k), shows a sharp peak, indicative of overscreening, at k~3^-1.