Theoretical Analysis Of Bonding Mechanisms In The Ionic Clusters Containting Noble Gas And Noble Metal

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⁺å’ŒAgXe₄²⁺. 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.