Zhao Gao-feng, Zhi Li-li, Guo Ling-ju, Zeng Zhi
School of Physics and Electronics, Henan University, Kaifeng 475004, People's Republic of China.
J Chem Phys. 2007 Dec 21;127(23):234705. doi: 10.1063/1.2805384.
Equilibrium geometries, charge distributions, stabilities, and electronic properties of the Ag-adsorbed (SiO(2))(n) (n=1-7) clusters have been investigated using density functional theory with generalized gradient approximation for exchange-correlation functional. The results show that the Ag atom preferably binds to silicon atom with dangling bond in nearly a fixed direction, and the incoming Ag atoms tend to cluster on the existing Ag cluster leading to the formation of Ag islands. The adsorbed Ag atom only causes charge redistributions of the atoms near itself. The effect of the adsorbed Ag atom on the bonding natures and structural features of the silica clusters is minor, attributing to the tendency of stability order of Ag(SiO(2))(n) (n=1-7) clusters in consistent with silica clusters. In addition, the energy gaps between the highest occupied and lowest unoccupied molecular orbitals remarkably decrease compared with the pure (SiO(2))(n) (n=1-7) clusters, eventually approaching the near infrared radiation region. This suggests that these small clusters may be an alternative material which has a similar functionality in treating cancer to the large gold-coated silica nanoshells and the small Au(3)(SiO(2))(3) cluster.
利用密度泛函理论并采用广义梯度近似处理交换关联泛函，研究了Ag吸附的(SiO₂)ₙ（n = 1 - 7）团簇的平衡几何结构、电荷分布、稳定性和电子性质。结果表明，Ag原子倾向于以几乎固定的方向与具有悬空键的硅原子结合，并且新来的Ag原子倾向于聚集在现有的Ag团簇上，从而导致Ag岛的形成。吸附的Ag原子仅引起其自身附近原子的电荷重新分布。吸附的Ag原子对二氧化硅团簇的键合性质和结构特征的影响较小，这归因于Ag(SiO₂)ₙ（n = 1 - 7）团簇的稳定性顺序趋势与二氧化硅团簇一致。此外，与纯的(SiO₂)ₙ（n = 1 - 7）团簇相比，最高占据分子轨道和最低未占据分子轨道之间的能隙显著减小，最终接近近红外辐射区域。这表明这些小团簇可能是一种替代材料，在治疗癌症方面具有与大的金包覆二氧化硅纳米壳和小的Au₃(SiO₂)₃团簇相似的功能。
