Classical inelastic scattering in Li+H2: A comparison of different potential energy surfaces

Abstract

Four different ab initio calculations were used to determine four sets of potential energies at a common set of geometries for the Li+H₂ collision system. The four calculations involved choices between a moderate and a large basis set and between the Hartree–Fock and the multiconfiguration‐self‐consistent field formalisms. Only the nonreactive ground electronic state surface was examined. An analytic functional form was least squares fit to each set of potential energies to produce four analytic potential energy surfaces. Classical trajectories at energies below the reaction threshold were run on each surface. The trajectories were analyzed to obtain the inelastic cross sections, differential cross sections, and average energy loss as a function of angle. The comparison of these collision observables from surface to surface was used to characterize the chemical accuracy of each surface. All four surfaces, from the least to the most accurate, produced significant amounts of rotational excitation.