（TiO2）n（n=3～8）团簇的几何结构和电子性质研究

Study on Geometric Structures and Electronic Properties of (TiO_2)_n(n=3-8) Clusters

采用广义梯度近似（GGA）方法，对（TiO2）。（n=3～8）团簇进行了结构优化，计算并分析了其几何结构，平均结合能，能级，态密度以及最高占据分子轨道．最低未占据分子轨道（HOMO．LUMO）的电子云密度分布。结果表明：随着n的增加，TiO2团簇（除了（TiO2），团簇外）的平均结合能都在逐渐缓慢增加。（TiO2）n（n=4～8）团簇的HOMO-LUMO能隙随n的增大而减小，而HOMO能量随n的增大而增加。（TiO2）n（n=3～8）团簇的HOMO的电子云主要集中在悬挂及连接的氧原子上，相反，LUMO上的电子云主要集中在钛原子以及少量部分氧原子上。

Based on generalized gradient approximation（GGA） method, the structures of （TiO2 ） n （ n = 3 - 8 ） clusters were optimized. Geometric structures, average binding energy, energy levels, density of states and electron density distributions of HOMO and LUMO were calculated and analyzed. The result indicate that （TiO2）n（n =3-8） clusters have a gradual increase in the average binding energy except （TiO2）7 cluster. Besides ,the HOMO-LUMO energy of （TiO2）n （n =4-8）clusters show a relatively decrease with the growing of the number. However, the HOMO energy is in keeping with the growing of the number n. The results indicate that the HOMO electron densities of （TiO2）n （n = 3-8）cluster were localized mostly around the oxygen atoms of suspension bond and connection bond. In contrast, the LUMO electron densities of （TiO2）, （n = 3-8） cluster are localized mostly around Ti atoms and some oxygen atoms.