SURFACE MELTING OF ICE

The present theories of surface premelting are based on the assumed me chanism whereby a liquid layer is formed because the free energy of th e surface is thus minimized. It is shown experimentally here that this mechanism is not possible in the case of ice, for which surface melti ng below 0 degrees C is, however, well documented. A mechanism of surf ace melting, unique for ice, is then proposed. It is based on a concep t according to which the surface phase equilibrium temperature differs from that of the bulk material. The new theory predicts the onset tem perature of premelting on ice in quantitative agreement with recent ex perimental data. It also explains regelation of ice and explains why w ater reaches a density maximum above its freezing point.