Theoretical Studies On The Au Clusters, Au Nanotubes And Calixarene Molecular Crystal

The thesis is structured as below: Chapter 1 is a general introduction about computational methods based on the density functional theory. In Chapter 2, we have investigated the structures of small Au clusters using empirical methods.In Chapter 3, we have found that Au_N, N=32,33,34,35 clusters can surprisingly have cage-like structures, which are stabilized by the strong relativistic effect. The stability of the icosahedral cage of Au₃₂ is confirmed by the ultra-soft and PAW pseudo-potential method (VASP), relativistic ADF and Dmol3 codes. Such an icosahedral cage would provide another interesting kind of cluster other than carbon fullerenes for further studies. We find that Au₃₂ and Au₃₄ could have large HOMO-LUMO gaps. As for Au₃₂ the gaps should originate from the high symmetry, while for Au₃₄, it is due to the close electronic shells of the clusters. We have also modified the traditional Jellium model into a spherical shell model, which highly indicates the Au₃₂ should have close electronic shells as well.In Chapter 4, we have also studied the structural properties of Au nanotubes, which are remarkably different from those of Carbon nanotubes. Au(n,n) can transit to Au(2n,n) under an axial compression.In Chapter 5, we have investigated the mechanism of the solid-solid phase transition from ABCD bi-layers to ABAB bi-layers of calixarene crystal after absorbing the vinyl bromide, and the diffusion of the vinyl bromide in the calixarene crystal.