DFT study of size-dependent geometries, stabilities and electronic properties of Si2Agn clusters: comparison with pure silver clusters

Abstract

The equilibrium geometric structures, stabilities and electronic properties of Si2Agn (n = 1–8) and pure silver Agn (n ≤ 10) clusters have been systematically investigated by using meta-generalised gradient approximation. Due to sp3 hybridisation, the lowest energy structures of Si2Agn clusters for n > 2 favour the three-dimensional structure. The silicon atoms prefer to be located at the surface of the host silver clusters. By analysing the relative stabilities, it is found that the di-bridged structure Si2Ag2 isomer is the most stable structure for Si2Agn (n = 1–8) clusters. The highest occupied–lowest unoccupied molecular orbital gaps, exhibiting a pronounced even–odd alternation, indicate that the doped clusters with even number of atoms have enhanced chemical stability than those with odd number of atoms. The results of Wiberg bond indices and electronic localisation function show that the stronger Si–Si and Si–Ag interaction may be the main driving force for the higher stability of Si2Agn clusters.