Density Functional Theory Study Of The NiMg_n,ZrB_n Clusters

In this thesis, the geometrical structures, electronic properties of NiMgn, ZrBn (n=1-12) clusters have been investigated with Density Functional Theory (DFT). The main contents are presented as the followings:The geometry structures, frequency and electronic properties of the NiMgn (n=1-12) clusters have been studied with the generalized gradient approximation (GGA) based on the density functional theory (DFT). The results indicate that the ground state structures and the electronic properties of the host Mgn+1clusters are changed obviously due to the encapsulation of Ni atom. As n≤8, the growth patterns of the ground state structures of the NiMgn clusters are dominated by the trigonal bipyrmid, as well as the octahedron structures. The evolution behaviors of the ground state structures based on the trigonal prism of the host clusters are partly modified from n≥9. The 3d,4p orbital of the Ni atom for different size clusters play the distinct roles in the s-p-d orbital hybridizations. The NiMg6 cluster, with higher symmetry Oh, is not only possession of improved stability, but also of the smallest energy gap (just about 0.25 eV) among all of the NiMgn clusters.The geometries, stabilities, electronic properties as well as the magnetism of ZrBn (n=1-12) clusters have been theoretically investigated with generalized gradient approximation (GGA) using PW91 functional based on density-functional theory. It was found that the nest-like structures dominated the growth pattern of ZrBn clusters starting from n≥9. The magnetic moment of B atoms of ZrB3 cluster exhibits the antiferromagnetic alignment incontrast to that of the ferromagnetic alignment of other clusters as n is odd numbers. The Zr atom easily keeps the comparatively larger magnetic moment due to the relatively higher symmetries of ZrB3 (C2v) and ZrB7 (C6v).