Effect of surface vacancies on the adsorption of Pd and Pb on MgO(100)

Theoretical quantum mechanical calculations have been carried out to establish the effect of surface vacancies on the adsorption of Pd and Pb atoms on the defective MgO(100) surface. The investigated defects included neutral, singly and doubly charged O and Mg vacancies on the (100) surface of MgO. These vacancies played the role of F-s (n+) and V-s (n-) (n = 0, 1, 2) adsorption centers for a single Pd or Pb atom. From the results of calculations, it is clear that the Pd- and Pb-atom adsorption at the F-s (n+) and V-s (n-) centers shows different characteristics than at the regular O2- and Mg2+ centers. Drastic changes in geometric, energetic, and electronic parameters are evident in Pd/V-s (n-) and Pb/V-s (n-). The effect of F-s(0) and F-s(+), which in practice are the most important vacancies, is smaller, yet the adsorption of Pd and Pb at these centers is more energetically favorable than at the regular O2- center. Of the two metals studied, the atom of Pd is bound by the F-s(0) and F-s(+) centers with higher adsorption energies. [GRAPHICS] .