First principle study of the sensitivity of CO adsorption on pure and binary clusters of lead and silicon

Abstract

The interactions of a CO molecule with pure and binary clusters of Pb and Si up to five atoms are theoretically investigated. The lowest-energy isomers of metal cluster carbonyl complexes are obtained by global optimization of the potential energy hypersurface using Monte Carlo simulation coupled with simulated annealing followed by pseudopotential based plane wave density functional theory (DFT) calculations, and then by local optimization using hybrid DFT calculations at the B3LYP/ aug-cc-pVTZ-pp level of theory. The CO binding energies and Gibbs free energy changes (ΔG) are computed to determine the kinetic and thermodynamic stability of the metal cluster-CO complexes. The variations of adsorption energy, HOMO-LUMO energy gap, and NBO charge on the CO fragment with the size of the metal clusters are reported. The linear correlations among different parameters such as C–O bond elongation, changes in the C–O stretching frequency, and NBO charge on CO are established to confirm the CO adsorption on various pure and binary clusters of Pb and Si.