Integration of the classical equations of motion on ab initio molecular potential energy surfaces using gradients and Hessians: application to translational energy release upon fragmentation

Abstract

A new method for calculating classical trajectories on molecular ab initio potential energy surfaces is presented. The equations of motion are integrated on a sequence of model surfaces constructed from analytically calculated molecular gradients and Hessians. The method avoids the explicit calculation of the total surface and is therefore applicable whenever the gradient and Hessian can be calculated. The method is applied to the unimolecular fragmentations of H 3 and CH 2OH +, yielding the translational energy released upon separation of the products.