Computational Aspects of Potential Energy Surfaces

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In this project in the Physical Chemistry Program, McIver will develop methods aimed at efficiently evaluating Born-Oppenheimer potential energy surfaces. The results will be used in computing polyatomic rate constants, including tunnelling effects, for a number of reactions involving radicals and biradicals using Variational Transition State Theory. The critical bottleneck in such calculations is the evaluation of the Reaction Path Hamiltonian which underlies virtually all currently used polyatomic rate theories. Three lines of attack on this bottleneck will be pursued: development of a formalism which explicitly relates the Reaction Path Hamiltonian coordinates (the reaction path and transverse vibration) and coupling constants to potential energy derivatives; development of techniques for speeding up the calculation of potential energy surfaces using self consistent field wavefunctions; and implementation of the methods on a distributed memory parallel computer. The computer codes will be developed with the aid of symbolic algebra software and a parallel computer simulator, both of which operate on a modestly configured workstation.