Systematic Theoretical Study on Structural, Stability, Electronic, and Spectral Properties of Si2MgnQ (Q=0, ±1; n=1-11) Clusters of Silicon-Magnesium Sensor Material

By using CALYPSO searching method and Density Functional Theory (DFT) method at the B3LYP/6-311G (d) level of cluster method, a systematic study of the structures, stabilities, electronic and spectral properties of Si(2)MgnQ (n = 1-11; Q = 0, +/- 1) clusters of silicon-magnesium sensor material, is performed. According to the calculations, it was found that when n > 4, most stable isomers in Si(2)MgnQ (n = 1-11; Q = 0, +/- 1) clusters of silicon-magnesium sensor material are three-dimensional structures. Interestingly, although large size Si(2)MgnQ clusters show cage-like structures, silicon atoms are not in the center of the cage, but tend to the edge. The Si(2)Mg1,5,6,8-1 and Si(2)Mg13,4,7,9,10+1 clusters obviously differ to their corresponding neutral structures, which are in good agreement with the calculated values of VIP, AIP, VEA, and AEA. |VIP-VEA| values reveal that the hardness of Si2Mgn clusters decreases with the increase of magnesium atoms. The relative stabilities of neutral and charged Si(2)MgnQ (n = 1-11; Q = 0, +/- 1) clusters of silicon-magnesium sensor material is analyzed by calculating the average binding energy, fragmentation energy, second-order energy difference and HOMO-LUMO gaps. The results reveal that the Si(2)Mg30, Si(2)Mg3-1, and Si(2)Mg3+1clusters have stronger stabilities than others. NCP and NEC analysis results show that the charges in Si(2)MgnQ (n = 1-11; Q = 0, +/- 1) clusters of silicon-magnesium sensor material transfer from Mg atoms to Si atoms except for Si(2)Mg1+1, and strong sp hybridizations are presented in Si atoms of Si(2)MgnQ clusters. Finally, the infrared (IR) and Raman spectra of all ground state of Si(2)MgnQ (n = 1-11; Q = 0, +/- 1) clusters of silicon magnesium sensor material are also discussed.