STATIC NONLOCAL DIELECTRIC FUNCTION OF LIQUID WATER

The wave vector dependent longitudinal static dielectric function epsi lon(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 ep silon(k) determined from neutron diffraction data. It exhibits a decre ase at small k, two divergence points on the k axis with a range of ne gative values in between, and the correct physical limit, epsilon(k -- > infinity) = 1. The response function, 1 - 1/epsilon(k), shows a shar p peak. indicative of overscreening, at k similar to 3 Angstrom(-1).