A COMBINED MOLECULAR-DYNAMICS AB-INITIO STUDY OF H-2 ADSORPTION ON IDEAL, RELAXED, AND TEMPERATURE-RECONSTRUCTED MGO(111) SURFACES

2D periodic ab initio calculations have been performed for H-2 interac ting with a temperature-reconstructed MgO(lll) surface, created from a molecular dynamics (MD) simulation at 300 K. The temperature effects involve both a long-time reconstruction of the surface and instantaneo us vibrational displacements. Chemisorption energies of similar to 60 mu J/mol were found. Comparisons with adsorption on ideal and relaxed MgO(lll) slabs show that the physi- and chemisorption properties for t he H-2/MgO(111) system are very sensitive to small topological details in the surface structure. The large surface reconstruction at 300 K i nvolves drastic changes of the surface's adsorption properties. We als o find that a low coordination number of the surface ions is not suffi cient to make the site attractive for chemisorption. (C) 1998 American Institute of Physics. [S0021-9606(98)50136-5].