Monte Carlo Calculations. VI. A Re-evaluation of the RRKM Theory of Unimolecular Reaction Rates

Abstract

Previously obtained Monte Carlo rate constants for unimolecular decomposition of model molecules [J. Chem. Phys. 40, 1946 (1964)] are compared with the predictions of a modified version of the Rice‐Ramsperger‐Kassel‐Marcus theory. The principal modification is an unambiguous method of specification of the critical value of the reaction coordinate. Anharmonicity corrections are accurately calculated, and an improved way of treating rotational state densities, closely related to that of Marcus [J. Chem. Phys. 43, 2658 (1965)], is used. The agreement between theory and Monte Carlo results is drastically improved; remaining deviations are about ± 50% for bent molecules and undetectable (within 20%) for linear ones.