Nonorthogonal tight-binding study 0f Si60 cluster

The lowest-energy structure of Si60 cluster is obtained by using a genetic algorithm (GA) based on nonorthogonal tight-binding (NTB) model. The atoms are organized into two shells. The outer shell forms a distorted cage consisting of 50 atoms and the inner shell with 10 atoms. The inner shell is looser than the outer shell. The density of states (DOS) and the HOMO-LUMO gap are also given. The Si60 fullerene cage structure and network structure are also studied using molecular dynamics annealing based on NTB model. It is found that the cage structure of Si60 is not stable, the network structure is stable, although it is not the lowest-energy structure. The single point energies on the different structures are also calculated by using ab initio method at B3LYP/LANL2DZ level and Kwon's tight binding model. Although the total energy differences obtained by these two methods are not same, both of them confirm that the energy of the structure obtained by NTB-GA is the lowest.