【作者】 李靓靓；

【导师】 赵永芳；

【作者基本信息】 哈尔滨工业大学 ， 凝聚态物理， 2010， 硕士

【摘要】 水包合物（clathrate hydrates）是由主体水笼和包含在水笼中的客体气体分子组成的，其中主体水笼由氢键连接的水分子构成。目前水包合物储存和运输氢气的作用得到了广泛的关注。本课题的理论基础是分子轨道从头算，使用自洽场（HF）方法和多种电子相关方法，例如二阶微扰论（MP2）、耦合簇（CCSD（T））、密度泛函（DFT）等方法并应用6-311++G**基组，由浅入深的研究了水包合物H2-（H₂O）₁₂的结构和稳定性，以及氢气客体被主体水笼捕获和从水笼内逃逸的可能性。研究的具体内容和得到的主要结果如下：重点在B3LYP/6-311++G**水平下研究了水笼团簇（H₂O）₁₂的成键机制及稳定性，并分析了水笼团簇（H₂O）₁₂的几何结构、解离能、H₂O分子间相互作用等内容。结果表明H₂O分子间非近邻相互作用导致了水笼团簇（H₂O）₁₂的收缩；在对水笼团簇（H₂O）₁₂研究的基础上，对水包合物H₂-（H₂O）₁₂的结构和稳定性进行了研究。同时分析了水包合物的各项性质，计算得到的结果表明主体水笼与客体氢气分子之间存在弱相互作用，因此在常温常压下其稳定性要高于水笼团簇；在关于水包合物的结构和稳定性研究的基础上，进一步研究了氢气客体是否能在水笼中迁移及水包合物形成后是否能将氢气释放出来的相关动态问题。应用电子结构计算确定了氢气在水包合物中迁移的势垒。计算了氢气分子从水笼中心通过六边形面迁出的一维势能曲线图。在MP2水平下应用6-311G*基组计算的势垒为2.751kcalmol-1。这个势垒可用于估算氢气由水笼中逃逸的速率，同时需要考虑逃逸速率的隧道效应。研究显示氢气在水包合物中的迁出能够发生并且动力学因素对于决定水包合物的结构和储氢能力十分重要。更多还原

【Abstract】 The clathrate hydrates is made up with the host water cage which is linked byhydrogen-bonded and guest gas molecules . At present, more and more attention havepaid on the use of storing and transporting by the clathrate hydrates for H2.In this paper, the theoretical basis is ab initio method of molecular orbit al theory,the method is self-consistent field and electronic structure calculations, investgatingthe structure and stability about water cage cluster （H₂O）₁₂ and the possibility of theguest H2 molecular capturing and escaping by the host water cage at HF, MP2,CCSD（T） and DFT level with 6-311++G** basis set.Investigate the Bonding mechanism and stability at B3LYP/6-311++G** levelemphasizely, and analysis the geometry, dissociation energy and interaction betweenmoleculars and so on. The result indicated the interaction between non-neighborsmoleculars lead to shrinkage for water cage cluster（H₂O）₁₂.At the basic of the study about the water cage （H₂O）₁₂, meantime studying thestructure and stability of the clathrate hydrates H2-（H₂O）₁₂. To analyze the respectivefeature of the clathrate hydrates, the result indicate that the weak interaction existsbetween the host water cage and the guest H2 molecules .So the stability of theclathrate hydrates H2-（H₂O）₁₂ is stronger than the water cage （H₂O）₁₂ at normaltemperature and pressure.At the basic of the structure and stability of clathrate hydrates, open questions inthe study are whether the H2 guest molecules can migrate between the clathrate cagesand whether H2 is released from the clathrate once it is formed. Electronic-structurecalculations are used to estimate the energy barriers to the escape of H2 guestmolecules from the cages of the clathrate hydrates. We have calculated theone-dimensional energy profile towards to the H2 molecules moving from the cagecenter through the center of hexagonal faces. The energy barriers calculated at theMP2 level with the 6-311G* basisi set are 2.751kcalmol-1. The energy barriers areused to estimate the escape rates from the cage, tunneling contributions to the escaperates are also considered at the same time. These studies indicate that H2 can migratethrough clathrate hydrates and that kinetic considerations can be very important indetermining the structure and H2-storage capacity of clathrate hydrates.更多还原