A combined reaction class approach with integrated molecular orbital plus molecular orbital (IMOMO) methodology: A practical tool for kinetic modeling

We present a new practical computational methodology for predicting thermal rate constants of reactions involving large molecules or a large number of elementary reactions in the same class. This methodology combines the inte grated molecular orbital+molecular orbital (IMOMO) approach with our recent ly proposed reaction class models for tunneling. With the new methodology, we show that it is possible to significantly reduce the computational cost by several orders of magnitude while compromising the accuracy in the predi cted rate constants by less than 40% over a wide range of temperatures. Ano ther important result is that the computational cost increases only slightl y as the system size increases. (C) 2000 American Institute of Physics. [S0 021-9606(00)00201-4].