Viii Cluster Element Base Structure Of The Mixed Clusters, Stability, And Magnetic Study

Nanocluster have became the foundation of developing new nanometer materials, while metal clusters are becoming a matter of concern for more and more people because the practical use in modern industry, especially for transition metal cluster. The base of high and new technological material is study for their structures and properties. In this paper we mainly perform an extensive study the structures and electronic properties as well as magnetism for Nin,Pdn,Ptn,clusters up to n=9, the neutral and cationic clusters of Al-doped Nin,Pdn,Ptnup to n=8 by using a density-functional-theory(DFT).1.Theoretical study of geometrical evolution and magnetism of group-â…§clustersIn this chapter, we take up an extensive study on the evolution of structures, electronic properties and magnetism for Nin, Pdn, Ptn, clusters up to n=9 by using a density-functional-theory(DFT). The calculated results show that we can quickly find a series of stable structures of Nin, Pdn, Ptn clusters by adding corresponding atom on the stable structures of Nin-1, Pdn-1, Ptn-1 clusters. Nin,Pdn,Ptn clusters have the same evolution of structure.We can get the stable structures of clusters by adding atoms on triangle and tetragon when n=2-6, the stable structures of clusters can be found by adding an atom on octahedron and decahedron when n>6, and the structures have gradually the cage configuration with the increase of size.The average bond length and coordination number increase with the increase of size, this indicate that the stable structures of clusters get balance with the working together of bond length and coordination number. The average bond length of Ni is the smallest, and Pd and Pt are near with the increase of size, and the average bong length of Pd is greater than Pt in addition to n=3,4.The binding energies of Ni-Pd-Pt clusters increase with the increase of size. The binding energies of Pd cluster are lowest, Pt cluster is maximal, and Ni cluster is slightly larger than Pd. The second difference in energy, the first derivative of the energy and HOMO-LUMO gap of Ni-Pd-Pt clusters don't show obvious parity oscillatory behavior with the increase of size. The stabilization energies reveal that Ni5 and Ni7, Pd2 and Pd4, Pt2,Pt5 and Pt8 are the relatively most stable in this series.The study of magnetism for Nin, Pdn and Ptn clusters indicates that the average magnetic moment/atom of Nin and Ptn are larger than Pdn, but that of Nin, is more than slightly larger than Ptn. Magnetic moment/atom of Ni-Pd-Pt clusters has been trending down with the increase of size, but that of Pdn and Ptn clusters reduces quickly.2.Structures, stabilities and magnetism of Al-doped Nin, Pdn, Ptn, clustersThe structural evolution, stabilities, electronic properties and magnetism of small neutral and cationic NinAl, PdnAl, PtnAl (n=1-8) clusters are investigated using DFT. Our study results predict the existence of a number of previously unknown isomers and structures. All structures may be derived from a substitution of a Ni (or Pd or Pt) atom by an Al atom in the stable structures Nin+1(Pdn+1 or Ptn+1) cluster. The most stable structures of NinAl cluster have the similar configurations with the ground state structures of Nin+1 cluster besides n=6. The most stable structures of the neutral PdnAl cluster have the same framework with the minimal-structures of Pdn+1 cluster besides n=3,6,8 and PtnAl cluster have the same structure with Ptn+1 cluster besides n=2,8. Compared with the neutral cluster, most of the corresponding structures of cationic clusters keep basically similar frameworks with the neutral clusters, while a few of the order of clusters energies has been changed. The findings indicate that the effect of the positive charge on NinAl, PdnAl, PtnAl are small.The study for bond length and coordination number of the impure clusters indicate that the stable structures of clusters get balance with the working together of Ni-Ni, Pd-Pd, Pt-Pt and Ni-Al, Pd-Al, Pt-Al bonds. The strong Ni-Ni, Pd-Pd, Pt-Pt bonds decide the framework of Ni, Pd, Pt, and the strong Ni-Al, Pd-Al, Pt-Al bonds make the Al atom in the high coordination number.The analysis for atomic averaged binding energies demonstrates that joining Al atom don't change the evolution trend of averaged binding energies of Ni-Pd-Pt clusters, which indicate that the stabilities of the neutral and cationic NinAl, PdnAl, clusters have been proved simultaneously as compared with the corresponding pure clusters, but the stabilities have been reduced for the neutral and cationic PtnAl clusters. The stabilities of neutral Ni5Al, Ni7Al and cationic Ni4Al+, Ni5Al+,Ni6Al+ clusters are higher than other clusters, which are different from the magic numbers 5 and 7 of pure Nin cluster. Pd3Al and Pd3Al clusters have more stabilities than other clusters, which are same with the magic cluster Pd4. The study for the Al-doped Pt clusters indicate that the stabilities of Pt2Al, Pt4Al, Pt6Al and Pt3Al+ are higher than other clusters, and the higher stability cluster Pt4Al don't change the magic number properties of Pt5.The study for magnetic properties of the impure clusters indicates that the Al-doped Nin, Pdn, Ptn clusters don't change the evolution trend of atomic magnetic moment of pure clusters, but decrease the magnetic moment of clusters which originate the effective charge transferring from Al to Ni(Pd or Pt) atoms.