The transfer of kinetic units (atoms or groups of atoms) in amorphous materials from one quasiequilibrium position to another quasi-equilibrium position is governed by the fluctuations of both the energy and the entropy of the system. In the glass transition range of liquids, the entropy mechanism plays a dominant role: fluctuations of the particle packing appear to be more significant than the accumulation of the energy. At high temperatures above the glass transition range, the energy mechanism plays a decisive role. The physical meaning of the parameter involved in the Bartenev equation relating the relaxation time to the cooling rate at the glass transition temperature is discussed. A technique is proposed for calculating this parameter with allowance made for the temperature dependence of the activation energy in the liquid-glass transition range. A variant of the modification of this equation is considered.

The fraction of the fluctuation volume (in a model of the excited state) at the glass transition tem perature depends linearly on the Gruneisen parameter, i.e., the degree of the anharmonicity of lattice vibra tions in amorphous polymers and glasses.

The Gruneisen parameter of glassy polymers and inorganic glass is a linear function of the fraction of the fluctuation volume that is frozen at the glass transition temperature. The nature of an interrelation between linear and nonlinear properties of solids, in particular, between the Gruneisen parameter and Pois son's ratio is discussed. F F m r 0 0 x m = Δr m x = r -r 0

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