PHENOMENOLOGICAL MODEL OF CRYSTAL AMORPHOUS PHASE-CHANGE

The concept of a transition to an amorphous state as the process of relaxation of a metastable crystalline phase with a higher free energy than the amorphous state is presented. The relaxation is considered as a process of heterogeneous nucleation and growth of amorphous grains in a metastable crystalline matrix. The crystalline phase can be metastable either because of a large defect concentration or because of a non-equilibrium crystalline structure. The assumption of the existence of long-lived crystal-like clusters in a liquid is important for a description of the liquid-glass transition. It is shown that the free energy of a mixture of a gas-like liquid and crystal-like clusters near the melting temperature can be lower than that of a pure gas-like liquid. The quantity of these clusters increases with cooling and the percolation region corresponds to the glass transition interval. © 1990 Elsevier Science Publishers B.V. (North-Holland).