A First-Principles Study of Sn Dimer Adsorbed on MgO Surface

A detailed characterization of metal clusters bound at the surface of crystalline metal oxide supports is crucial for identifying their structure–property relationships relevant to practical applications. Theoretical investigations based on first-principles calculations have proven to be helpful in characterizing supported metal clusters. In this work, the adsorption of an Sn dimer on the regular and defective (100) surfaces of MgO crystal was studied by means of density functional theory (DFT) calculations. The investigated defects included Fs0, Fs+, and Fs2+ oxygen vacancies on MgO(100). From the results of the calculations, it is clear that the adsorption of Sn2 at the Fs0 and Fs+ centers is stronger than that occurring on the defect-free MgO(100) surface. While the triplet spin multiplicity of a free Sn dimer tends to be preserved upon its adsorption at the Fs2+ center, spin quenching is favored for the dimer adsorbed at the regular O2− and defective Fs0 and Fs+ centers. The topological analysis of the electron density for the adsorbed dimer was carried out within the quantum theory of atoms in molecules (QTAIM). The calculated values of QTAIM parameters for the Sn-Sn bond of the adsorbed dimer do not differ radically from the corresponding values for the dimer in the gas phase.