Adsorption of CO on the rumpled MgO(100) MgO(100):Ni, and MgO(100):Cr surfaces:: A density functional approach

We investigated the adsorption of carbon monoxide on the MgO(100), MgO(100):Ni, and MgO(100):Cr surfaces, using an ab initio density functional cluster embedding approach. The relaxation and rumpling of the MgO surface were explored through potential energy curves. Then, the Mg adsorption site of sharp and rumpled surfaces was studied. Both local density and generalized gradient approximations were employed, and the orbitals were expanded as Gaussian atom-centered orbitals. It was found that the surface relaxes bulkward similar to 1.4%, but Mg ions displace more toward the bulk than the oxygen ions, producing a surface rumpling of similar to 0.95%. The energy obtained for CO adsorption on the pure MgO surface with the generalized gradient approximation using the Perdew-Wang (PW86) functional was as large as 1.6 kcal/mol. Finally, for all the systems studied in this work, the relaxed-rumpled surfaces showed a surface-CO adsorption energy larger than the sharp surfaces. (c) 2005 Wiley Periodicals, Inc.