Application of the theory of dispersion forces to the surface melting of ice.

Abstract

We apply the theory of Dzyaloshinskii, Lifshitz, and Pitaevskii to ice, water, and vapor at the triple point and find that electromagnetic interactions do not permit a liquid film of macroscopic thickness at the ice-vapor interface. Hence the surface melting of ice is at most incomplete. However, the thickness of the film which is permitted is surprisingly large, with retardation effects setting the scale. Our estimate is about 30 \AA{}. Further liquid appears as droplets with a contact angle of about 0.2\ifmmode^\circ\else\textdegree\fi{}. The film thickness decreases rapidly with temperature.