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Dr. Kamal Amal Kamal Soliman :: Publications:

Title:
Adsorption and spin state properties of Cr, Ni, Mo, and Pt deposited on Li+ and Na+ monovalent cation impurities of MgO (001) surface: DFT calculations
Authors: Ahmad S Shalabi, Mervat M Assem, Kamal A Soliman
Year: 2011
Keywords: Adsorption . Cr, Ni, Mo, and Pt adatoms . Density functional theory (DFT) . Li+ and Na+ cation impurities . MgO (001) surface . Spin states
Journal: J Mol Model
Volume: 17
Issue: Not Available
Pages: 3299–3308
Publisher: springer
Local/International: International
Paper Link: Not Available
Full paper Kamal Amal Kamal Soliman_j.mol.mod2011.pdf
Supplementary materials Not Available
Abstract:

We have analyzed, by means of density functional theory calculations and the embedded cluster model, the adsorption and spin-state properties of Cr, Ni, Mo, and Pt deposited on a MgO crystal. We considered deposition at the Mg2+ site of a defect-free surface and at Li+ and Na+ sites of impurity-containing surfaces. To avoid artificial polarization effects, clusters of moderate sizes with no border anions were embedded in simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The interaction between a transition metal atom and a surface results from a competition between Hund's rule for the adsorbed atom and the formation of a chemical bond at the interface. We found that the adsorption energies of the metal atoms are significantly enhanced by the cation impurities, and the adsorption energies of the low-spin states of spin-quenched complexes are always more favorable than those of the high-spin states. Spin polarization effects tend to preserve the spin states of the adsorbed atoms relative to those of the isolated atoms. The metal– support interactions stabilize the low-spin states of the adsorbed metals with respect to the isolated metals, but the effect is not always enough to quench the spin. Spin quenching occurs for Cr and Mo complexes at the Mg2+ site of the pure surface and at Li+ and Na+ sites of the impurity-containing surfaces. Variations of the spin-state properties of free metals and of the adsorption and spinstate properties of metal complexes are correlated with the energies of the frontier orbitals. The electrostatic potential energy curves provide further understanding of the nature of the examined properties.

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