Preexponential Factors for Elementary Surface Processes

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Abstract
Theoretical calculation of the rate of an elementary physicochemical process represents a rather complicated procedure. This holds both for the description of dynamics of the interaction on the atomic level and for the statistical averaging over all the possible initial states of the system under investigation. It is important that under thermal equilibrium, one can express the rate of many elementary processes on the basis of potential energy surfaces (PES) for the motion of the atomic nuclei, exploiting the transition state theory (TST) [1]. Using this theory, one can estimate for a given PES the preexponential factor (PEF) of the rate constant in most cases with a precision of the order of magnitude. The TST has been worked out more than 50 years ago and it represents one of the principal bases of chemical kinetics. Many attempts to generalize the standard TST have been published (see e.g., Ref. 2). However, these generalizations and improvements of the standard TST are usually not essential from the practical point of view (excluding, of course, approaches worked out for the description of processes, in which the fundamental assumptions of TST are not applicable).