【作者】 张平霞；

【导师】 赵永芳；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2009， 博士

【摘要】 惰性气体原子电子结构稳定,化学活性小,化学成键问题一直倍受人们的关注。贵金属原子,物理化学性质也比较稳定。因此,惰性气体和贵金属原子的成键问题是化学键理论的一道难题,由惰性气体和贵金属原子形成的小分子、团簇是国内外研究的焦点。并且,含惰性气体贵金属的混合/掺杂团簇的微观结构特点和奇异的物理化学性质为制造和发展特殊功能的新材料开辟了新的途径,在催化科学、表面科学、纳米科学与技术、基于团簇制造特殊功能材料等领域中具有广泛的应用前景。迄今为止,国内外已经在理论和实验上报导了一些包含惰性气体-贵金属键的新颖化合物、团簇和块状晶体。人们惊讶地发现一些惰性气体-贵金属化学键相对比较强,并不是以微弱的范德瓦耳斯力结合。因此,探索惰性气体-贵金属键的成键机制,发展研究含惰性气体-贵金属键的体系的理论和方法,发现其重要的物理、化学性质,以及不断完善该类物质的研究体系等,成为人们的重要研究内容。本文基于量子化学、结构化学、原子与分子物理学、群论、团簇物理学等基础理论,在分子轨道理论的框架下,使用了考虑“电子相关效应”和“相对论效应”的计算方法,重点研究了若干含惰性气体-贵金属键的分子和离子小团簇的惰性气体-贵金属键的成键机制,其次对几何结构、电子结构、稳定性、分子内的相互作用、以及团簇的尺寸效应等方面也进行了系统地考察。本文使用二阶微扰论方法（MP2）,通过对惰性气体-贵金属键的分析,预言了惰性气体-贵金属氢氧化物NgMOH （Ng =Ar,Kr,Xe;M = Au,Ag,Cu）是化学上稳定的化合物,有可能被人工合成。研究发现:所研究体系的惰性气体-贵金属键与以范德瓦耳斯力结合的化学键相比,键长比较短,解离能比较大,成键比较稳定。其成键机制比较复杂,电荷诱导能、色散能、贵金属氢氧化物上多极矩的贡献、共价相互作用等都对该化学键的形成起了重要作用。惰性气体和贵金属之间存在电荷转移,贵金属是电荷的受体。惰性气体-贵金属氢氧化物是一种可能稳定存在的化合物,本文为实验合成该化合物提供了重要的理论依据。通过对Au-Ar化学键的分析,确定了掺杂金离子的氩的系列团簇Au⁺Ar_n （n = 1-6）的“幻数”结构Au⁺Ar₄和Au⁺Ar₆。本文采用密度泛函方法（B3LYP）优化了团簇的各种可能初始几何构型,确定了能量最低的基态结构,并在此基础上,研究了团簇的稳定性随着氩原子数目增加的变化规律,确定了团簇第一个闭合壳层的“幻数”结构。结果发现:由于团簇的Au-Ar键比Ar-Ar键稳定,该团簇的基态稳定构型倾向于Au⁺离子在中心,其它的Ar原子逐渐包围在Au⁺周围,形成最多的Au-Ar键。在这些团簇序列中,当Ar原子数目为4和6时,团簇比较稳定。6个Ar原子形成团簇的第一个闭合壳层。Au⁺Ar4是畸变的四面体结构,Au⁺Ar6是八面体结构。通过对四方平面结构的含惰性气体贵金属离子团簇的成键分析,发现静电相互作用和相对论效应是影响惰性气体和贵金属离子化学成键的重要因素。本文使用了二阶微扰论（MP2）方法考虑了电子相关效应,使用相对论的赝势（RPP）和非相对论的赝势（NRPP）考虑了相对论效应,研究了四方平面结构的包含氙和高氧化态的金离子的AuXe₄²⁺团簇,并首次推广到铜、银体系,进一步确定这类四方平面结构的化合物是否适合于CuXe₄²⁺和AgXe₄²⁺。结果发现:MXe₄²⁺ （M = Cu,Ag,Au）团簇的惰性气体-贵金属键的解离能按照Cu–Ag–Au的顺序不断增大。虽然,Cu-Xe和Ag-Xe键没有Au-Xe键强,但是,它们也很稳定。静电相互作用对二价的惰性气体-贵金属键的形成起了重要作用。相对论效应使M-Xe键的键长变短、解离能增加,从而使团簇更加紧凑和稳定。频率分析表明这种四方平面结构适合于AuXe₄²⁺和AgXe₄²⁺,而对于CuXe₄²⁺,稍微发生畸变的三维立体结构更稳定。更多还原

【Abstract】 Noble gas atoms have stable electronic configuration, and are less reactive. So chemical bonding has attracted the considerable attention of chemists and physicists. For noble metal atoms, their physicochemical properties are also unexpectedly stable. Thus, the bonding between noble gas and noble metal brings forward a considerable challenge toward the classical chemical bond theory, and the molecules and clusters containing noble gas and noble metal become the focus of investigations. Furthermore, the characteristics of microstructures and novel physicochemical properties of mixed/doped clusters containing noble gas and noble metal atoms break another way to make and develop the new special functional materials. They have wide and valuable applications in catalysis, superficies, nanoscience and technique, special functional materials based on clusters and so on. So far, many novel compounds, clusters and bulk crystals containing noble gas–noble metal bonding have been reported theoretically and experimentally. It is surprisingly found that partial intra-molecular noble gas–noble metal bonds are relatively strong, which are not bonded by the weak van der Waals force. Therefore, it is important to explore the bonding mechanism of noble gas–noble metal bonds, develop new theories and methods to investigate the compounds containing noble gas and noble metal atoms, find their important physicochemical properties, and make studies of preceding species further systematize and so on. On the basis of Quantum Chemistry, Structural Chemistry, Aotm and Molecule Physics, Group Theory, Cluster Physics etc., the noble gas–noble metal bonding mechanism is mainly investigated, and the geometric and electronic structures, stabilities, intra-molecular interactions, the size effect of clusters and so on are also studied by using the computational methods in the framework of molecular orbital theory, which account for the electronic correlation and relativistic effects.Noble gas–noble metal hydroxides NgMOH （Ng = Ar, Kr, Xe; M = Au, Ag, Cu） have been predicted to be chemically stable compounds, which are possible to synthesize in the experiments, at the MP2 theoretical level. It is found that the noble gas–noble metal bond lengths are shorter and the corresponding dissociation energies are larger, as compared to those of the van der Waals complexes. The noble gas–noble metal bonding mechanisms are complicated. Charge-induction energies, dispersion interaction, the effects of MOH monomers, covalence, etc., play an important role in the chemical bonding of above species. A certain amount of charge transfer takes place between noble gas and noble metal atoms, and noble metal atoms behave as acceptor of electrons. The NgMOH species are sufficiently stable and would be possible to be prepared and well-characterized in the experimentsAu⁺Ar4 and Au⁺Ar6 magic structures of gold ion-doped argon clusters Au⁺Arn （n = 1-6） have been confirmed by the analysis of Au-Ar chemical bonds. In order to confirm the global minimum energy stable structures, various possible starting geometries are considered during the geometry optimization by using B3LYP method. Furthermore, based on them, the evolution of relative stabilities with the size of clusters is investigated to confirm the“magic numbers”of first closed shell. The results show that, for Au⁺Arn, Au–Ar bonds are stronger than Ar–Ar bonds, so the argon atoms tend to gradually arrange around the central gold ions, allowing the maximum Au–Ar bonds to be formed. In the cluster series, comparatively stable complexes are considered to consist of four and six argon atoms. The Au⁺Ar6 is the first shell closure of clusters. The most stable structure of Au⁺Ar4 is distortedly tetrahedral, and that of Au⁺Ar6 is octahedral.By the bonding analysis of square-planar clusters containing noble gas and noble metal, it is found that the electrostatic interactions and the relativistic effects play an important role in the chemical bonding of noble gas and noble metal. In this paper, the MP2 method accounting for the electronic effects, and the relativistic and nonrelativistic pseudopotentials （RPP and NRPP） accounting for the relativistic effects, are emplyed to investigate the square-planar AuXe₄²⁺ cluster containing noble gas and high oxidation state gold ion. Then, these species are expanded to Cu and Ag systems to find out whether this class of compounds is suitable for CuXe₄²⁺和AgXe₄²⁺. The results indicate that the dissociation energies of M–Xe bonds in the square planar MXe₄²⁺ （M = Cu, Ag, Au） systems, become larger and larger along the sequence Cu–Ag–Au. The copper and silver evidently tend to be weakly bonded to the noble gas atoms in comparison with gold. But, they are still stronger bonds. The electrostatic interactions have a large effect on the divalent M–Xe chemical bonds. The relativistic effect evidently decreases the bond distances, increase the dissociation energies and makes the cluster compact and stable. The vibrational frequencies analysis indicates that the square planar stable structure is only suitable for the AuXe₄²⁺ and AgXe₄²⁺. For CuXe₄²⁺, the slightly distorted three-dimensional D2d structure is more stable than the square-planar structure.更多还原