FLUCTUATIONAL MODEL OF MELTING

Processes occurring in a real solid crystal - i.e., a crystal containi ng lattice defects in thermal disequilibrium - close to the melting po int are considered. On approaching the melting point, uniform and nonu niform fluctuations of the deformation and the order parameter develop in a solid crystal; the mean square of some of these fluctuations ten ds to infinity at the melting point, so that we may speak of the fluct uational nature of melting, The basic conclusion is that the processes developing in a solid crystal on approaching the melting point result in a limiting stable state, which is spinodal, i.e., it satisfies the condition (partial derivative P/partial derivative V)(T) = 0. From th is state, the body passes in equilibrium fashion to the liquid phase. The body cannot be superheated on melting, since phase transition occu rs from the limiting (spinodal) state. Thus, the melting curve is dete rmined by the equation (partial derivative P/partial derivative V)(T) = 0. Experimental data on acoustic emission close to the melting point are consistent with this theoretical perspective.