Structures,stabilities, and electronic properties of F-doped Sin （n=1～12） clusters：Density functional theory investigation

The geometries, stabilities, and electronic properties of FSin （n=1～12） clusters are systematically investigated by using first-principles calculations based on the hybrid density-functional theory at the B3LYP/6-311G level. The geometries are found to undergo a structural change from two-dimensional to three-dimensional structure when the cluster size n equals 3. On the basis of the obtained lowest-energy geometries, the size dependencies of cluster properties, such as averaged binding energy, fragmentation energy, second-order energy difference, HOMO–LUMO （highest occupied molecular orbital–lowest unoccupied molecular orbital） gap and chemical hardness, are discussed. In addition, natural population analysis indicates that the F atom in the most stable FSin cluster is recorded as being negative and the charges always transfer from Si atoms to the F atom in the FSin clusters.     

三视图还原多面体的一个简便方法

三视图还原空间几何体的学习,是培养和考查学生空间想象能力的重要途径.学生需要仔细观察、多角度分析才能揭开空间几何体的“庐山真面目”.相对于旋转体而言,多面体的还原更加困难.近几年的三视图题型多考查多面体的还原,且很多是“不常规放置”的多面体的还原.如果仅凭空间想象,学生很容易陷入困境.很多教师都提到借助长方体和正方体作为背景模型进行多面体还原,是一种方便有效的方法.     

Structure,stability and electronic properties of SrSi_n(n= 1–12) clusters::Density-functional theory investigation

Geometric structures, stabilities, and electronic properties of SrSin(n = 1–12) clusters have been investigated using the density-functional theory within the generalized gradient approximation. The optimized geometries indicate that one Si atom capped on SrSin 1structure and Sr atom capped Sinstructure for difference SrSinclusters in size are two dominant growth patterns. The calculated average binding energy, fragmentation energy, second-order energy difference, the highest occupied molecular orbital, and the lowest unoccupied molecular orbital(HOMO–LUMO) gaps show that the doping of Sr atom can enhance the chemical activity of the silicon framework. The relative stability of SrSi9is the strongest among the SrSinclusters. According to the mulliken population and natural population analysis, it is found that the charge in SrSin clusters transfer from Sr atom to the Sinhost. In addition, the vertical ionization potential, vertical electron affinity, and chemical hardness are also discussed and compared.