Ab initiostudy of the symmetric reaction path ofH2with a surfaceVcenter in magnesium oxide

Abstract

An all-electron ab initio calculation, including correlation effects, of the symmetric reaction path of ${\mathrm{H}}_2$ with a surface $V$ center in magnesium oxide has been carried out. The importance of lattice relaxation effects has been demonstrated, and the position of the saddle point has been located. The calculated barrier to the reaction, 40 kcal ${\mathrm{mol}}^{-1\mathrm{}}$, is considerably greater than the value necessary for ${\mathrm{H}}_2$-${\mathrm{D}}_2$ exchange at 78 K, suggesting that the lowest-energy pathway involves the asymmetric interaction of ${\mathrm{H}}_2$ with the surface $V$ center.