Density-functional theory study of structures,stabilities, and electronic properties of the Cu2-doped silicon clusters: Comparison with pure silicon clusters

Equilibrium geometric structures, stabilities, and electronic properties of Si_nCu₂ (n=1–8) clusters and pure silicon Si_n (n=3–10) clusters are investigated systematically by exchange-correlation density functional (B3LYP). The optimized geometries show that the most stable isomers have 3D structure for n=2, 4–8, and Cu-substituted Si_n+2 clusters is dominating growth pattern for the Si_nCu₂ clusters. The calculated averaged binding energies, fragmentation energies, second-order difference of energies, and the HOMO–LUMO gaps show that Si₂Cu₂ and Si₅Cu₂ clusters have enhanced relative stabilities and chemical stability than their neighboring clusters. Electronic properties of Si_nCu₂ (n=1–8) clusters are studied by calculating the natural population analysis and electrostatic potential, where the results show that the two copper atoms always possess positive charge and positive potential surround them. In addition, the VIP, VEA and the chemical hardness (η) are also analyzed and compared.