Abstract: Two new structures of cage (terminal cage) and ring for silica clusters (SiO2)nO2H4 (n＝2～22, n is even) are presented and compared with line structure. Geometric structures, average binding energies, energy gaps and second order difference of energy are systematically studied by density function theory (DFT) B3LYP with basis set 6-31G(d). The results indicate that for cage structures of (SiO2)nO2H4 (n＝2～22, n is even) magic number clusters exist not only at n=4, 8, but also at n=14. Ring structures of (SiO2)nO2H4 clusters are different from that of (SiO2)n. For the latter they are more stable than line structures from n=11. However, for the former it is from n=4 ring structures begin to be more stable than line structures. It means that the addition of water has an important effect on the stabilities of silica clusters.

Key words: Cluster, Magic number, Density functional theory, Structure, Mechanism