AN INTERPOLATED UNRESTRICTED HARTREE-FOCK POTENTIAL-ENERGY SURFACE FOR THE OH-2-]H2O+H REACTION(H)

In this paper we demonstrate, at the UHF/6-311 + + G(d,p) level of the ory, the practical feasibility of using a Initio quantum chemical calc ulations to generate a molecular potential energy surface (PES) for th e OH+H-2-->H2O + H reaction using our previously suggested interpolati on and iteration schemes. The successful, and almost completely automa ted, merger of the PES algorithm and quantum chemical calculations inv olves a number of significant practical problems, the solutions of whi ch are presented in detail. The convergence of the interpolated potent ial surface was monitored in terms of reaction probability and we find that the surface converges once the energy, gradient and Hessian have been calculated at approximately 350 geometries. We also find that, a lthough the initial geometries used consisted only of points along a r eaction path for the OH+H-2-->H2O + H reaction, the potential energy s urface iteration process rapidly adds information about other, energet ically accessible, reaction channels. (C) 1996 American Institute of P hysics.