Heterolytic adsorption of H-2 on ZnO(10(1)over-bar-0) surface: An ab initio SPC cluster model study

Heterolytic adsorption of H-2 On ZnO(10 (1) over bar 0) surface has been in vestigated by means of ab initio embedded cluster method. The embedding poi nt charges are spherically expanded, while the values of the spherical char ges are determined to be self-consistent with those of the atoms in the clu ster. Several possible adsorption sites have been considered with Zn5O5 and Zn4O4, which are the stoichiometric clusters having the least amount of da ngling bonds in the given size. The effect of the shape of the embedding sp herical charge array and the influence of the surface reconstruction on the calculated adsorption properties have been investigated. The calculation r esults show that the heterolytic adsorption of H-2 on ZnO(10 (1) over bar 0 ) surface is site-dependent, taking place only on those Zn-O ion-pairs with low coordination numbers, such as Zn-2c-O-3c, Zn-3c-O-2c, and Zn-2c-O-2c, rather than on the perfect ion pair, Zn-3c-O-3c. The calculated adsorption heats, as well as vibrational frequencies of the Zn-H and O-H bonds, are in reasonable agreement with the experimental values.