The effect of silicon doping on the geometrical structures, stability, and electronic and spectral properties of magnesium clusters: DFT study of SiMgn (n=1-12) clusters

摘要

Using the density functional theory (DFT) method at the B3LYP /6-311G (D) level, we studied how silicon doping affects the geometrical structure, stability, and electronic and spectral properties of magnesium clusters. The stable isomers of SiMgn (n = 1-12) clusters were calculated by searching numerous initial configurations using the CALYPSO program. The geometrical structure optimization shows that most stable SiMgn (n = 3-12) clusters are three-dimensional. In addition, geometrical structure growth patterns show that some structures of SiMgn clusters can be directly formed by replacing one Mg atom in the corresponding Mgn + 1 cluster with one silicon atom, such as SiMg8 and Mg-9 clusters. The stability of SiMgn clusters is analyzed by calculating the average binding energy, fragmentation energy, and second-order energy difference. The results show that SiMgn clusters with n = 5 and 8 are more stable than others. MO contents analysis show that the Si 3p-orbitals and Mg 3s-orbital are mainly responsible for the stability of these two clusters. The results of NCP and NEC analysis of electronic properties reveal that the charges in SiMgn (n = 1-12) clusters transfer from magnesium atoms to silicon frame, and electronic charge distributions are primarily governed by s- and p-orbital interactions. In addition, the VIP, VEA, and chemical hardness of ground sates of SiMgn (n = 1-12) clusters were studied in detail and compared with the experimental results. The conclusions show that the chemical hardness of most SiMgn clusters are lower than that of pure Mgn + 1 (n = 1-12) clusters, except for n = 1 and 8. This indicates that the doping of silicon atom can always reduce the chemical hardness of pure magnesium clusters. Finally, the infrared and Raman spectral properties of SiMg5 and SiMg8 clusters were calculated and discussed in detail.