DEVELOPMENT OF THE ACTIVATION PROCESS MODEL - COMPENSATION EFFECT

In this article, an attempt was made to develop an activation process model. The average energy of the translational motion of the atoms, ta king part in the elementary activation process and being in the thermo dynamic equilibrium with thermal radiation, was obtained using the qua ntum canonical Gibbs distribution and the model principles of elementa ry activation. The degeneracy and exclusion of some excited vibrationa l levels were taken into consideration, the result being a strong depe ndence of the probability of surmounting the activation barrier on the behavior of the excited vibrational states of the quantum subsystems. As an application of the development model, the formulas of the preex ponential factor for solid-state atomic diffusivity and first-order ch emical reaction rate constants were derived. Quantitative analysis of the atomic diffusion in solids in the framework of our model has made it possible to describe the diffusion processes in metals, covalent se miconductors, as well as diffusion anomalies, connected with the ''non classical'' behavior of the empirical Arrhenius dependence. A possible physical essence of a kinetic compensation effect is discussed. It wa s shown that compensation may be caused by only changing the degenerac y of the vibrational levels of the quantum subsystems. (C) 1996 John W iley & Sons, Inc.