Optimized basis functions for coupled channel calculations

An earlier version of introducing optimized basis functions for reaction dynamics using coupled channel equations [W. Brenig, R. Brako, M.F. Hilf, Z. Phys. Chem. 197 (1966) 237] is generalized and simplified conceptually. Rather than beginning the procedure in the oscillator basis, we now start from a ‘single channel’ assumption to define a basis taking some of the dynamics of the variables perpendicular to the reaction path into account. Our earlier version using generalized oscillator states [W. Brenig, R. Brako, M.F. Hilf, Z. Phys. Chem. 197 (1966) 237] (‘quantum trajectories’) can easily be derived and generalized starting from the formalism presented here. The parameters of the quantum trajectories are now determined using Ehrenfestʹs theorem. onstrate the power of the method, we apply it to the corrugation problem in surface reactions. The use of optimized basis states again leads to a great reduction in basis size as compared to plane wave states.