Impurity-doped Si10 cluster: Understanding the structural and electronic properties from first-principles calculations

Structural and electronic properties of metal-doped silicon clusters (MSi₁₀, M=Li, Be, B, C, Na, Mg, Al, and Si) have been investigated via ab initio molecular dynamics simulation under the formalism of the density functional theory. The exchange-correlation energy has been calculated using the generalized gradient approximation method. Several stable isomers of MSi₁₀ clusters have been identified based on different initial configurations and their relative stabilities have been analyzed. From the results it is revealed that the location of the impurity atom depends on the nature of interaction between the impurity atom and the host cluster and the size of the impurty atom. Whereas Be and B atoms form stable isomers, the impurity atom being placed at the center of the bicapped tetragonal antiprism structure of the Si₁₀ cluster, all other elements diffuse outside the cage of Si₁₀ cluster. Further, to understand the stability and the chemical bonding, the LCAO-MO based all electron calculations have been carried out for the lowest energy isomers using the hybrid B3LYP energy functional. Based on the interaction energy of the M atoms with Si₁₀ clusters it is found that p-p interaction dominates over the s-p interaction and smaller size atoms interact more strongly. Based on the binding energy, the relative stability of MSi₁₀ clusters is found to follow the order of $C{Si}₁₀>B{Si}₁₀>Be{Si}₁₀>{Si}₁₁>Al{Si}₁₀>Li{Si}₁₀>Na{Si}₁₀>Mg{Si}₁₀$, leading one to infer that while the substitution of C, B and Be enhances the stability of the ${Si}₁₁$ cluster, others have an opposite effect. The extra stability of the $Be{Si}₁₀$ clusters is due to its encapsulated close packed structure and large energy gap between the HOMO and LUMO energy levels.