O. Weintraub et M. Bixon, ENTROPY OF REACTION AND NUMBER OF ACTIVE-MODES IN THE THEORY OF ELECTRON-TRANSFER REACTIONS, Journal of physical chemistry, 98(13), 1994, pp. 3407-3411
The entropy of reaction is incorporated in a classical model by introd
ucing frequency changes in the harmonic modes. Various properties, suc
h as the rate constant dependence on the energy of reaction and on the
temperature, are influenced by the number of active modes. This numbe
r is therefore an important parameter of the system. It becomes unimpo
rtant in the asymptotic limit, when its value is very large. In this l
imit one recovers the classical Marcus expression.