Influence of structure on reaction efficiency in surface catalysis. 3. Entropic and dynamical aspects

The authors introduce a general method for calculating (and predicting) the rate constant for a kinetic process in which a coreactant, migrating on the surface of a catalyst (or molecular organizate) having clusters of stationary reaction centers, undergoes an irreversible reaction upon first encounter. The authors method is based on the relationship between the first moment of the underlying probability distribution function governing the process (the mean walk length (n) of the diffusing coreactant), the (zero-mode) relaxation time of the system (the reciprocal of the smallest eigenvalue {lambda}{sub 1} of the stochastic mater equation for the problem) and a statistical (also information theoretic) expression for the entropy. Extensive calculations are reported for a wide variety of configurations of active sites (monomers, dimers, triplets, quartets, hexamers, and (binary and ternary) combinations thereof), and the efficiency of the diffusion-controlled reactive process is studied as a function of the concentration C{sub T} of reaction centers and a statistical order parameter {delta}.