THE ENERGETICS AND DYNAMICS OF H-2 DISSOCIATION ON AL(110)

We present a modeling of the sticking dynamics of H-2 on Al(110). The modeling is based on an ab initio calculation of the H-2/Al(110) potential energy surface. The calculation is done both within the local density approximation (LDA) and using non-local corrections via the generalized gradient correction (GGA). We find that the GGA increases the barrier for dissociation substantially, and that the inclusion of gradient corrections greatly influences the dissociation dynamics. The dissociation dynamics is simulated by first doing a full quantum mechanical calculation of the dynamics in two of the six H-2 coordinates, the distance of the molecule from the surface and the intra-molecular bond length. The other four degrees of freedom are then included using the hole model. This implies that these coordinates are treated classically, and in the sudden approximation. Test calculations in three dimensions, where full quantum calculations are feasible, show the hole model to work well for the onset of sticking. Finally, the full six-dimensional sticking calculations are compared to the results of molecular beam experiments, both for pure and seeded beams.