B5H5的结构和性能研究

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摘要采用密度泛函理论(DFT)中的杂化密度泛函（B3LYP）方法，在6-31G基组基础上对B5H5团簇进行了几何结构的全方位优化。在优化得到的多种稳定的几何结构中，选取能量最低的构型作为B5H5团簇的基态结构。并在基态结构的基础上计算研究B5H5团簇的物理和化学性能。主要结论如下：59530

（1）通过优化B5H5的几何构型，得到了B5H5团簇的多种稳定构型，其中构型为C1对称以及自旋多重度为1的三维立体结构的结合能量最低，并将其作为B5H5的基态结构。

（2）通过对B5H5基态结构稳定性的分析，得到其化学活性强，分子不稳定，容易被激发，热力学稳定性和化学稳定性较弱。

（3）2p轨道上B原子的电荷分布最多，在B5H5团簇的B原子内部和原子之间都会发在生s、p轨道杂化、电荷转移。

（4）B5H5比B2H6中电子结构的稳定性相对减弱，而原子之间的成键作用和离域效应都相对增强。B5H5比B2H6的各向异性不变量显著增大，则对外场的各向异性响应增大，B5H5团簇的体密堆积性弱于B2H6。

（5）在红外光谱中，B5H5团簇位于波数1332cm-1频率处的峰值最大，相应的红外强度最大，该处的振动模式为呼吸振动。波数频率范围在2600~2900cm-1之间的振动峰的峰值相差不大，相应的振动强度也相差不是很大，其振动模式为伸缩振动。在拉曼光谱中，处于波数2116cm-1频率处的振动峰的峰值最大，其活性最强。

（6）由HOMO图发现，B5H5团簇的电离能低，便于失去电子，容易发生亲电反应；由LUMO图来看，B5H5团簇电子亲核势高，便于得到电子，发生亲核反应。

（7）当试探原子Bq位于B5H5团簇空间几何构型的中心(0.000 nm)位置和试探原子到平面的垂直距离为0.025 nm、0.050 nm、0.075 nm、0.100 nm位置时，计算得到的NICS值全为负，则B5H5团簇在这五个位置均具有芳香性。芳香性最强的位置在试探原子Bq到平面的垂直距离在0.075 nm处。NICS值随着垂直距离的增大先减小后增大，表明芳香性先增大后减小，B5H5中可能拥有多重芳香性。

毕业论文关键词：B5H5团簇；密度泛函理论；物理化学性能

Abstract Density functional theory (DFT) of the hybrid density functional theory (B3LYP) method in the 6-31G basis set on the basis of a full range of B5H5 clusters optimized geometry. In various stable geometry optimization obtained, select the lowest energy configuration as the ground state of B5H5 clusters. On the basis of the calculation of the ground state of the physical and chemical properties B5H5 research clusters. The main conclusions are as follows:

(1) By optimizing the B5H5 geometry, Got more stable structures B5H5 clusters, which configuration is C1 symmetry and spin multiplicity of binding energy of the lowest three-dimensional structure of 1, and as B5H5 ground state structure.

(2) Through the structural stability of the ground state B5H5 analysis, Obtain its chemical activity, unstable molecules, easily excited, thermodynamics and chemical stability of the weak.

(3) Distribution charge up to 2p orbital on atom B, and between B atoms and atomic B5H5 internal clusters are made in student s, p orbital hybridization, charge transfer.

(4) B5H5 relatively weakened stable than B2H6 electronic structure and bonding between atoms and the role of isolated domains relatively enhanced. B5H5 than B2H6 anisotropy invariants in significant increases, the anisotropy in response to the external field increases, B5H5 body close-packed clusters weaker than B2H6.

(5) In the infrared spectrum, B5H5 clusters located in the largest peak wave number 1332 cm-1 frequency, maximum intensity corresponding infrared, where the vibration mode of vibration of breathing. The wave number frequency range of the peak vibration peak 2600 ~ 2900 cm-1 is little difference between the corresponding vibration intensity difference is not great, the vibration mode of stretching vibration. In the Raman spectrum at the peak maximum vibration peak wave number 2116 cm-1 frequency, its most active.