Dissociation and sticking of H-2 On the Ni(111), (100), and (110) substrate

The adsorption, dissociation, and sticking of H-2 on the N(111), (100), and (110) substrates are studied with spin-polarized gradient corrected densit y functional theory. To parametrize the six-dimensional (6D) potential ener gy surface (PES), between six and twelve two-dimensional sections of the PE S are calculated using density functional theory. For the interpolation bet ween such 2D sections, a scheme is developed and tested predicting the ener gy of the H-2 molecules with an accuracy of about 50 meV in low-symmetry si tes. On the interpolated 6D PES, classical simulations of the H-2 sticking coefficient are performed, and the results are compared with experiment. Th e important experimental trends are well reproduced, and a simple model is discussed to explain why dissociation is activated on the (111) surface and nonactivated on the rough (110) surface. The results are compared to those for H-2 on Pd, and it is shown that the difference between Ni and Pd stems mainly from the surface s electrons.