Novel structure and electronic property of Sin (21⩽n⩽30) clusters

Using first-principles simulated annealing generalized gradient approximation density functional calculations based on norm-conserving pseudopotentials, we have investigated the geometric and electronic structures of low-energy silicon clusters (Sin, n=21–30). We have obtained new low-energy structures not reported previously. Our calculations suggest that the lowest energy structures are spherical ones including core atoms whose number increases with the cluster size. The trend of the binding energy as well as that of the energy difference between the highest occupied and the lowest unoccupied molecular orbitals is studied as a function of the cluster size and the number of core atoms.