Eur. Phys. J. D (2015) 69: 244
https://doi.org/10.1140/epjd/e2015-60404-1

Regular Article

A density functional study of small sized silver-doped silicon clusters: Ag₂Si_n (n = 1–13)^*

¹ Department of Computer Science and Information Technology, Nanyang Normal University, Nanyang 473061, P.R. China
² Department of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061, P.R. China

^a e-mail: zhangshuai@nynu.edu.cn
^b e-mail: nynulucheng126@126.com

Received: 14 July 2015
Received in final form: 25 August 2015
Published online: 5 November 2015

Abstract

The structures and electronic properties for global minimum geometric structures of small-sized neutral Ag₂Si_n (n = 1–13) clusters have been investigated using the CALYPSO structure searching method coupled with density functional theory calculations. A great deal of low-energy geometric isomers are optimised at the B3LYP / GENECP theory level. The optimised structures suggest that the ground state Ag₂Si_n clusters are visibly distorted compared with the corresponding pure silicon clusters and favor a three-dimensional configuration. Starting with Ag₂Si₁₂, one Ag atom is fully encapsulated by the Si outer cages. Based on the averaged binding energy, fragmentation energy, second-order energy difference and HOMO-LUMO energy gap, it is seen that Ag₂Si₂ and Ag₂Si₅ are tested to be the most stable clusters, and the chemical stabilities of pure Si_n+2 clusters can be reduced to some extent after doping two Ag atoms. Additionally, natural population and natural electronic configuration are discussed and the results reveal that charges transfer from the Ag atoms to the silicon frames and the spd hybridisations are present in all Ag₂Si_n clusters. Lastly, the results of natural bonds show that the Ag-Si bond in Ag₂Si_n clusters is dominated by small ionic character.