Theoretical Study On The Structure And Properties Of Metal And Semiconductor Clusters

The structures and stability of the ground-states for Cu13-nAgn(n≤l3) and Rhn, Ptn (n=2-20) clusters have been studied by Gupta model potential based on tight binding second moment approximation in combination with a genetic algorithm(GA). An exchange operator is introduced in GA for study of the multi-element clusters. For Cu13-nAgn(n≤13) clusters, it is found that the most stable structures of the pure clusters (n=0,13) are perfect icosahedron, and the structures for the mixed clusters (n=l-10) have stable structures which are slightly deformed with respect to the perfect icosahedron. The Cu atom prefers to occupy the center of the clusters with higher coordination numbers. As the number of Ag atoms increase, the average distance between the closest atoms in the Cu13-nAgn clusters increased monotonously, and the average binding energy of the ground-states decreased monotonously. The structure of Rhn, Ptn clusters for n≤13 are very similar and both of these two kinds of clusters have a tendency evolving to icosahedron. For larger clusters when n>13, the structures of Ptn show disorder characteristic but Rhn keep in order structure. With the increasing of cluster size, the total binding energies and coordination numbers for Rhn,Ptn(n=2-20) clusters increase monotonously. According to the second differences of binding energies, the magic numbers for Rhn,Ptn(n=2-20) clusters are n=4,6,13,15.Possible geometrical structures and relative stability of semiconductor microclusters GanPn(n=1-5) are studied by using density functional calculations with generalized gradient approximation (B3LYP). For the most stable isomers of GanPn(n=1-4) clusters, the electronic structures, vibrational properties, dipole moments, polarizability and ionization potential are analyzed using HF, MP2, CISD and B3LYP methods with different basis sets. For Ga5P5 cluster, the most stable structure is a cube-based structure. The calculation of the density of states for Ga5P5 shows semiconductor-like property. The IR and Raman spectra, the dipole polarizability anisotropy invariant and hyperpolarizability are also calculated.