【作者】 高晨阳；

【导师】 徐灿；

【作者基本信息】 兰州大学 ， 光学， 2006， 硕士

【摘要】 团簇是构成纳米材料的基本单元,对其几何结构和电子结构的研究已经成为新材料微观结构设计中的重要课题。硅氧化物的广泛应用以及相应纳米材料的特殊性质,使得人们对硅氧团簇研究产生了浓厚兴趣。在过去十几年里,硅氧团簇的结构和性质已经有了大量的理论研究,一方面验证了实验结果,另一方面也为实验提供了理论指导。本论文在实验基础上,通过密度泛函理论（DFT）中的B3LYP方法结合不同的基组对二氧化硅离子团簇进行了理论研究。全文主要分以下三个部分: Ⅰ.（SiO₂）_nX^-离子团簇结构和稳定性的理论研究 主要研究（SiO₂）_nX^-（n=1～5 X=_,O,OH）离子团簇的三类典型结构（三元环结构、二元环链状结构和四面体笼状结构）。本章利用密度泛函理论B3LYP结合基组6-311+G^*的方法对离子团簇的几何结构、平均结合能、能隙以及拉普拉斯电荷密度进行了分析。并推测幻数团簇（SiO₂）₄O₂H₃^-的形成可能依赖于（SiO₂）₄OH^-的结构。 Ⅱ.中性幻数团簇（SiO₂）₈O₂H₄结构的密度泛函理论研究 主要研究了中性幻数团簇（SiO₂）₈O₂H₄的七种代表性结构。用密度泛函理论的B3LYP方法结合6-31+G^**基组结构进行优化计算,并对各种结构的稳定性进行分析。得出双笼结构和立方笼结构为能量相对较低的两种结构构型,而能隙结果进一步表明,这两种结构容易反应形成较大的团簇类型。 Ⅲ.离子团簇（SiO₂）₄O₂H₃^-到（SiO₂）₈O₂H₃^-的生长机制研究 主要对离子团簇（SiO₂）_nO₂H₃^-（n=4～8）提出了两种生长机制。通过密度泛函理论的B3LYP结合基组6-31+G^**的方法对（SiO₂）_nO₂H₃^-（n=4～8）以及相应中性团簇（SiO₂）_nO₂H₄（n=4～8）的两类几何构型进行优化,研究其平均结合能以及能量的二阶差分随n值的变化规律,并分析了两类构型的最高占据轨道,从而肯定了这两种增长方式合理性。更多还原

【Abstract】 The atomic cluster is one of elementary building unit which form nanometer material. Its geometric structure and electronic structure have become an important topic in the design of the micro structure. Due to the wide application of silicon oxide and special nature of corresponding nanometer material, silicon oxide nanoclusters have drawn much attention. In the last decade, the properties of silicon oxide nanoclusters have been largely studied. On the one hand, it tests the results of experiment;on the other hand, it provides theoretical guidance for the experiment. Based on the experiment, we study silica anion cluster using DFT method. The full text contains the following three parts:Ⅰ. Study on the structure and stablities of anion cluster（SiO₂）_nX^-3MR （three-membered ring） structure, 2MR （two-membered ring） linear chain structure and pseudotetrahedral cage structure have been proposed for the anion cluster （SiO₂）_nX^-（n=1⁵ X=_, 0, OH）. The geometric structure, average binding energy, energy gap and Laplas density are performed by the DFT theory at the B3LYP/6-311+G* level. It is predicted that the formation of （SiO₂）₄O₂H₃^-may depend on the structure of （SiO₂）₄OH^-.Ⅱ. DFT theoretical study on the structure of magic clusterSeven typical structures of magic cluster （SiO₂）₈O₂H₄ are present. The stabilities of structures and energy gap have been analyzed using B3LYP with 6-31+G** basis set. It is confirmed that double-cage structure and cubic structure are more stable than others. The result of energy gap indicates that these two structures are inclined to form larger cluster.Ⅲ . The growth mechanism of magic cluster from （SiO₂）₄O₂H₃^- to （SiO₂）₈O₂H₃^-Two growth mechanisms from （SiO₂）₄O₂H₃^- to （SiO₂）₈O₂H₃^- are proposed.Geometrical structures are optimized via density function theory with 6-31+G** basis set. Average binding energy, the second-order energy difference and the orbital of HOMO are systematically discussed, which confirms that both growth mechanisms are reasonable.更多还原