金属氢化物的分子结构、分子反应动力学和Ni₄团簇的分子结构

【作者】 罗德礼；

【导师】 朱正和；

【作者基本信息】 四川大学 ， 原子与分子物理， 2002， 博士

【摘要】 ZrCo和LaNi₅是一类非常重要的贮氢材料，已经有非常充分的实验研究，然而，理论研究的报道不多。本文根据相对论有效原子实势和密度泛函理论方法（B3LYP／SDD与B3LYP／6-311G^*），用Gaussian-98W程序研究了ZrCo、ZrH、CoH、UH、Ni₂、AlNi、UH₂、HZrCo和Ni₃分子的分子结构、分析势能函数、微观力学性质和光谱性质；首次建立了计算固体金属氢化物体系宏观性质理论模型，并应用于ZrCo、Zr和Co的氢化反应体系研究，理论计算与实验结果基本一致；基于Monte-Carlo准经典轨线方法，首次研究了H与ZrCo和Co与HZr的分子反应动力学。从群的分解与直积理论和原子分子反应静力学原理出发，导出了Jahn-Teller效应引起Ni₄团簇分子的D_4h和T_d构型变化及其可能的电子状态。得到了如下主要研究结果： 1)根据原子分子反应静力学原理和群的直积、约化与分解理论，导出了双原子分子ZrH、CoH、UH和Ni₂的离解极限。根据相对论有效原子实势和密度泛函理论方法（B3LYP／SDD与B3LYP／6-311G^*），用Gaussian-98W程序计算确定了它们的基电子状态；用从头计算方法计算得到了这些分子的微观性质及分析势能函数，导出了分子的力常量和光谱常数。 2)根据原子分子反应静力学原理和群的直积、约化与分解理论，导出了UH₂、HZrCo、Ni₃以及AlNi₂的合理离解极限；根据相对论有效原子实势和密度泛函理论方法（B3LYP／SDD与B3LYP／6-311G^*），用Gaussian-98W程序计算确定了它们的基电子状态，得到了UH₂、HZrCo和Ni₃的微观几何、力学和光谱性质；分析了这些分子的三种基本振动模式，计算得到了其振动频率。基于多体项展式理论方法，研究得到了UH₂、HZrCo和Ni₃三原子分子的分析势能函数，这些分析势能函数正确反映了它们的结构特点，可用于研究HZrCo、UH₂和Ni₃的微观分子反应动力学。 3)从群的分解与直积理论出发，通过Jahn-Teller变形，vibronic相互作用以及群表示的分解的分析，首次导出了Jahn-Teller效应引起D_4h和T_d构型Ni₄分子几何构型变化及其可能的电子状态。采用密度泛函理论方法（B3LYP／6-311G） 网川人学博土学位论文对Ni4分子可能的几何构型进行了优化，得到了D4h、DZh、CZh、CZ、．、D。和CS六种构型Ni。分子的几何结构、能量，优化得到的分子构型的电子状态与山群论导出的结果一致，说明 Ni。的 Td和 D，＾构型的Jahn－Teller效应的确存在目．相当明显；在 Ni。分子的 D4h和 Td构型的不同畸变稳定构型中，多重性为 ZS刊＝7的能量最低，说明自旋激化在Ni。分子构型的变化中起到了重要作用。采用正则振动分析方法，分析了 Ni。分子的 D。、DZ。和 CZv三种构型的基态的正则振动方式，计算得到了各种振动方式的振动频率。4)基于量子力学和热力学基本理论，考虑到分子中电子和核运动的不同运动特点，首次建立了计算固体金属氢化物体系宏观性质的理论模型，建立起了分子微观性质和宏观性质间的联系。采用密度泛函理论方法（B3LYP沼DD）和该理论模型，结合必要的实验数据，计算得到了氢同位素气体（H卜D卜T＊与CO、Zr和ZrCo合金反应生成氢化物分子的能量E和嫡凡得到了Co、Zr和ZrCo与HZ、D。和乃反应的AHe、AGg禾f”，导出了 Co、Zr禾ZrCo与氢同位素气体反应的平衡压力与温度的关系。ZrH、CoH和ZrCoH的热力学函数及氢化反应的平衡压力的计算结果与实验结果有很好的一致性，表明这种近似模型是合理的。5）建立了三粒子碰撞反应体系的 Hamilton运动方程。用 Monte－Carlo准经典轨线方法，首次研究了W＊Sg)＋ZrCoO习和Co(／Fo卜ZrH碰撞反应体系，通过对方程组进行RKG法和AM法联合数值求解，得到在不同的初始平动能E下，散射粒子在各个反应通道上的分布、散射粒子的准经典轨线和散射角分布。利用分子反应动力学研究结果，探讨了ZrCo合金氢化反应中的歧化反应现象的机制。更多还原

【Abstract】 Density functional (B3LYP/SDD and B3LYP/6-311G*) method with relativistic effective core potential (RECP) have been used to optimize the microstructure of ZrCo, ZrH, CoH, UH, Ni2, AlNi, UH2, HZrCo and Ni3, and to calculate their energy, potential energy functions, as well as their force constants and spectroscopic data. The hydrogenating reactions systems for ZrCo, Zr, Co have been studied based on RECP. A model for the theoretical investigation of metallic hydrides has been put forwarded by author. The atomic and molecular reaction dynamic processes for the collision of H+ZrCo and Co+ZrH systems have been studied based on the present potential energy function of HZrCo and Monte-Carlo puasi-classical trajectory approach. Based on the analysis of the Jahn-Teller effect, vibronic interaction and the resolution of group representations, the possible geometrical configurations of Ni4 have been derived for the first time, the results are in good agreement with the calculation esults.Firstly, the reasonable dissociative limits for the diatomic molecules of ZrCo, ZrH, CoH, UH, Ni2 and AlNi have been derived based on the Atomic and Molecular Reactive Statics(AMRS) and the resolution of group representations. The ground electronic states, which are X2?, X3?, X4? and X3?u respectively for these molecules, have also been optimized based on the RECP method. The Murrell-Sorbie potential energy functions for the diatomic molecules have been obtained according to the ab inilio data through the least square fitting method. The spectroscopic data, force constants have been derived from the potential energy functions.Secondly, the reasonable dissociative limits for the tri-atomic molecules UH2. HZrCo, Ni3 and AlNi2 have been derived based on the Atomic and Molecular Reactive Statics(AMRS) and the resolution of group representations. The ground electronic states, which are X3A2, X5A2, X5A1 and X2B2 respectively for these molecules, have also been optimized based on the RECP method. The analytic potential energy functions for ground states of ZrCoH, UH2 and Ni3 molecules havebeen derived by many-boy expansion method using their equilibrium geometry structure parameters, dissociation energy and force constants. These potential energy functions, which show the structure characteristics of the molecules exactly, can be regarded as foundation for molecular reaction dynamic processes investigation.Based on the analysis of the Jahn-Teller effect, vibronic interaction and the resolution of group representations, the possible geometrical configurations of Ni4 have been derived for the first time. The Gaussian-98 program has been used to optimize the geometrical configurations of Ni4 based on B3LYP/6-311G method. It is found that there are at least six different stable geometrical configurations for Ni4. The results show that the multiplicity of 2S+1=7 for cluster Ni4 is the most stable state among the eight geometry configurations. The derived configurations are fair in agreement with the calculated results. It is means that the Jahn-Teller effect is very important in the geometry distortion of the A4h and Td configuration for Ni4.Then, the atomic and molecular reaction dynamic processes for the collisions of H+ZrCo(v=0,j/=0) and Co+ZrH(v=0,j=0) systems have been studied based on the present potential energy function of ZrCoH by Monte-Carlo puasi-classical trajectory approach. The results show that both H+CoH(v=0,j=0) and Co+ZrH(v=0.j=0) have no energy threshold. The results also show that the reaction section for H+ZrCo(v=0.j=0) decrease with the initial energy increasing. The molecular reaction dynamic processes for the collisions are mainly elastic scattering and non-reaction when the initial energy is over 200kJ/mol. The mechanism for the disproportion phenomena in the hydrating-dehydrating of the ZrCo alloy has been discussed.In the last section of the paper, a model for the theoretical investigation of metallic hydrides has been built for the first time by the author. Density functional (B3LYP/SDD) Method with Re更多还原