Reaction path zero-point energy from diffusion Monte Carlo calculations

Abstract

A general diffusion quantum Monte Carlo method is described for accurately calculating the zero-point energy of the vibrations orthogonal to a reaction path in a polyatomic system. The method fully takes into account anharmonic and mode–mode coupling effects. The algorithm is applied to the OH+H2→H2O+H reaction and the results are compared with a more approximate calculation. The technique will have many useful applications to kinetic and spectroscopic problems involving polyatomic molecules.