THE CALCULATION OF KINETIC ISOTOPE EFFECTS BASED ON A SINGLE REACTION-PATH

In this paper we propose a new method for calculating kinetic isotope effects without calculating a separate reaction path for each isotopic ally substituted species. The new method yields reasonable kinetic iso tope effects from calculations using the same reaction path for all is otopic variations. The method is tested by carrying out variational tr ansition state theory calculations, including multidimensional tunneli ng contributions, for the reactions OH+H-2-->H2O+H, CH3+H-2-->CH4 +H, and H+H-2-->H-2+H and nine deuterium-substituted isotopologs of these reactions. The results are very encouraging. (C) 1998 American Institu te of Physics. [S0021-9606(98)01139-8].