Density functional investigation on structural and electronic properties of small bimetallic Pb n Ag n (n=2–12) clusters

Abstract

Structural and electronic properties of Pb n Ag n (n=2–12) clusters were investigated by density functional theory with generalized gradient approximation at BLYP level in DMol3 program package. The optimized bimetallic Pb n Ag n (n=2–12) clusters were viewed as the initial structures, then, those were calculated by ab initio molecular dynamics (AIMD) to search possible global minimum energy structures of Pb n Ag n clusters, finally, the ground state structures of Pb n Ag n (n=2–12) clusters were achieved. According to the structural evolution of lowest energy structures, Ag atoms prefer gather in the central sites while Pb atoms prefer external positions in Pb n Ag n (n=2–12) clusters, which is in excellent agreement with experimental results from literature and the application in metallurgy. The average binding energies, HOMO-LUMO gaps, vertical ionization potentials, vertical electron affinities, chemical hardness η, HOMO orbits, LUMO orbits and density of states of Pb n Ag n (n=2–12) clusters were calculated. The results indicate that the values of HOMO-LUMO gaps, vertical ionization potentials, vertical electron affinities and chemical hardness η show obvious odd-even oscillations when n≤5, Pb n Ag n (n=2–12) clusters become less chemically stable and show insulator-to-metal transition with the variation of cluster size n, Pb n Ag n (n≥9) cluster are good candidates to study the properties of PbAg alloys. Those can be well explained by the density of states (DOS) distributions of Pb atoms and Ag atoms between–0.5 Ha and 0.25 Ha in Pb n Ag n (n=2–12) clusters.