Theoretical investigation on the adsorption of lithium atom on the Sin cluster (n=2-7)

Ab initio calculations are carried out to study the adsorption of Lithium atom on the Sin cluster with n ranging from 2 to 7. At the MP2/6-31G(d) level, the structures of the neutral Sin clusters and the SinLi clusters (n=2-7) are optimized. The single-point energy at QCISD/6-311+G(d,p) level for the optimized isomers are further performed. Harmonic vibrational frequency analysis at the MP2/6-31G(d) level is also undertaken to confirm that the optimize geometries are stable. Based on our results, the most favorable sites for Li adsorption on the Si2-7 clusters are the bridge sites. In addition, the vertical ionization energies of the SinLi clusters and the electron affinities of the Sin clusters are also calculated. The clear parallelism between the vertical ionization energies of SinLi and the electron affinities of Sin is found. This is consistent with the fact that the framework of the Sin in the SinLi cluster is similar to the structure of the corresponding negative ion Sin−.