Interpolated potential energy surface and classical dynamics for H₃⁺+HD and H₃⁺+D₂

Abstract

A potential energy surface for H₅⁺ has been constructed by a modified Shepard interpolation on a sparse set of data points, using second order Möller–Plesset perturbation theory. An improved version of the surface was also obtained by substituting the energy values at the data points with values evaluated using a coupled cluster treatment (with single and double excitations, and perturbative treatment of triple excitations). Classical simulations for the collisions between H₃⁺+HD and H₃⁺+D2 were carried out in order to calculate the total integral cross sections and rate coefficients for these systems. There is good agreement with earlier experimental data for rate coefficients at temperatures between 80 and 300 K, but the predicted rate coefficient for the reaction of H₃⁺+HD at 10 K deviates from the most recent experimental measurement, suggesting that quantum rather than classical reactiondynamics are necessary.