New implementation of the trajectory surface hopping method with use of the Zhu-Nakamura theory

A new implementation of the trajectory surface hopping (TSH) method is proposed to treat multidimensional nonadiabatic dynamics by incorporating the analytical Zhu-Nakamura semiclassical theory of nonadiabatic transition. The problem of classically forbidden hops in the TSH method can now be solved and dealt with just as easily as the classically allowed hops by introducing nonvertical hopping techniques. This is made possible, because the theory can treat both classically allowed and forbidden hops accurately in a unified way. The Zhu-Nakamura theory also enables us to predetermine important regions of potential energy surface before carrying out any dynamics calculations, and thus to save a lot of computational efforts. The charge transfer processes in the collinear H-3(+) system are studied numerically to test the new TSH method. Comparing the new and old versions of TSH with exact quantum calculations, the new method shows much better agreement with the exact calculations. It also works well when all trasitions are classically forbidden and the old method fails completely. (C) 2001 American Institute of Physics.