Theoretical Studies Of The Structures And Magnetic Properties On Platinum Doped Manganese And Aluminium Doped Niobium Clusters

Among numerous metal clusters, the alloy cluster, which contains magneticmetal elements, has attracted many researchers’ attention with its peculiar electronicstructure and magnetic properties. Further researches on them enable people tounderstand the peculiar identities of alloy clusters and to provide the theoreticalsupport for manufacturing and developing new materials of special performance. Thecluster structure’s variation and properties with the number of atoms is a basic subjectin cluster research. In experiments, many experimental techniques can only provideindirect information of cluster, and a large number of studies conducted by theoreticalcluster researchers show that simulation studies on the structure and properties ofclusters by means of computer theories can make up for the deficiency ofexperimental methods. Density Functional Theory (DFT), a new theoreticalcalculation method developed in recent years which converts complex N wavefunction and its corresponding Schrodinger Equation into simple electronic densityfunction, has become an effective and powerful tool to solve many difficult problemsin the theory of electronic structure.This thesis, by using density functional theory, conducts theoretical studies andcomputation of the mixture of small binary clusters of platinum-manganese andaluminum-niobium, with systematic studies on their micro-properties of geometricstructures, stability, electronic properties and electromagnetic characteristics as wellas these properties’ relationship and variation law with cluster sizes. The mainresearch contents and conclusions are as follows:I. Summary of cluster science. As a cluster’s size is between that of atom,molecule and macroscopic solid materials and has many unique properties, it is animportant object for experimental and theoretical studies. This thesis starts with briefintroduction of the main contents, research significance and development of clusterresearch, followed by brief introduction of the research purpose and the main researchcontent of this thesis.II. The second chapter chiefly introduces the basic framework of theoretical calculation method and development process, and the development process of densityfunctional theory and the two commonly used exchange-related functions.III. With Saunders Global Optimization kick Model and density functional theoryB3LYP hybrid method, this thesis makes a systematic study on the geometrystructure, electronic and magnetic properties of the cluster system of manganese atomdoped with pure platinum clusters PtnMn (n=2~6) on Lanl2dz basic cluster level, andthe computation of the local magnetic moments of platinum atoms and manganeseatoms in PtnMn clusters by using Natural population Analysis (NPA). Thecalculation result shows that the manganese atom doped in PtnMn (n=2~6) clustermakes its binding energy larger and the incorporation of manganese atom canimprove the stability of pure platinum clusters, thus the energy gap of HOMO-LUMOcluster has also undergone a significant change, and that the doping of manganeseatoms changes the chemical active of clusters. The local magnetic moment ofmanganese atoms mainly comes from the contribution of3D orbital electron, whichremains unchanged in the process of cluster size variation; the local magnetic momentof platinum atoms mainly comes from the contribution of5D orbital electron, whosecontribution to the total magnetic moment gradually increases.IV. Based on the DFT B3W91method, at the mixed basis set level, by using theGaussian09software, this thesis makes systematic theoretical study on the geometries,electronic and magnetic properties of NbnAl (n=1~10) binary alloy cluster. By usingDFT calculation method and introducing generalized gradient approximation and therelativistic effective core potential, this thesis also studies the relationship of cluster’sgeometric structure, binding energy, the second difference energy, HOMO-LUMOenergy gap and magnetic moment with cluster’s size variation. The resultsdemonstrate that the atom doped in NbnAl （1≤n≤10）cluster usually occupies thesurface of the clusters. The aluminum atom’s transition from capped structure toembedded structure does not take place until n=10. It is also found that the bindingenergy becomes smaller after doping of Al atom into Nb cluster. This may be due tothe respective bond energy differences of Nb-Nb bond and Nb-Al bond.