On the solid-liquid phase transition

Abstract

The mechanism by which fluidity is brought about and maintained is discussed. It is suggested that fluidity arises when sufficient energy is coupled from acoustic modes to fluid modes. The coupling mechanism involves the nonlinearity in an essential way, so that the critical amplitude of the acoustic modes necessary to initiate fluidity is analogous to the critical “pump” amplitude in a laser necessary to initiate the laser action. The Lindemann law for melting expressed in terms of a critical amplitude ratio of the acoustic vibrations becomes a natural consequence of the model. Since the model describes primarily the development of fluidity within a single phase, additional discussion is given to show the relationship to the customary interpretation of melting as a first-order phase transition between two independent phases.