Structural Predictions And Properties Of Clusters By Quantum/Molecular Mechanics

The clusters can widely found in nature and human practical activities, and cluster science is being developed as a new discipline between the atomic/molecular physics and solid state physics. The basic problems of clusters is to understand how clusters gradually evolved from atoms and molecules, and with this evolution, how the structure and properties of the clusters change.In this thesis, we have chosen the AU20and BeO units as the research object, and investigated the structures and properties of (AU20)N and (BeO)N clusters by using different theoretical calculation method.The main studies are as follows:1. Structural prediction of (Au2o)N (N=2-40) clusters and their building-up principleWe located the geometric structures of (AU20)N (N=2-40) clusters using the basin-hopping method and multiple-center Lennard-Jones model potential. Some magic number structures have been observed, among which (Au2o)s is a close-shell five-membered ring,(Au2o)20is a hollow-cage, and (Au2o)35is a double-cage in which the two cages share a five-membered ring. Moreover, the building-up principle of (Au2o)at clusters is significantly different from that of the other molecular or atomic clusters. The orientational effect on Au20-Au20potential is much greater compared to that on C60-C60potential.2. Researchs on Geometric and Electronic Structures of (BeO)N(N=2-12,16,20and24)The structure of (BeO)N clusters (N=2-12,16,20, and24) are investigated using the method combining the genetic algorithm with density function theory. The global minimum structures of (BeO)N clusters are rings up to N=5, double rings at N=6and7and cages at N≥8.Besides, almost all of the structures of (BeO)N cluster are aromatic according to the NICS criterion. Adaptive natural density partitioning analysis reveals that C6,(BN)3, and (BeO)3rings are similar in bonding patterns, C24and (BeO)12fullerenes are similar in bonding patterns. The building-up principle of (BeO)N is different from that of covalent (BN) and ionic (LiF and MgO) clusters.