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First-principles Study Of The Transition Atoms Doped Silicon Clusters

Posted on:2012-12-31Degree:MasterType:Thesis
Country:ChinaCandidate:Y Z BaiFull Text:PDF
GTID:2131330332495342Subject:Theoretical Physics
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In this thesis, uSi_ng first-principle quantum chemistry method based on Density-Functional Theory (DFT), we study the Tb atom and other transition metal atoms (Y, Pd, La, Yb, Lu) doped into the Si_n clusters. The geometric structures, electronic and magnetic properties are discussed.The main content is as follows: On the one hand, the growth behavior of small Si_n(n=2-14) and the doped Tb clusters are systematically studied by uSi_ng the density functional theory(DFT) within the generalized gradient approximation(GGA) as implemented in Dmol~3. The calculate results show that, from n=4, the silicon clusters grow into three dimensionally(3D) and prefer to form compact structures. As the calculation results and discussion about the average binding energies, fragmentation energies and the energy gaps(HOMO-LUMO), we find that the doping of the Tb atoms has greatly stabilize the pure silicon clusters. Besides, from the Mulliken populations(MP) and magnetic properties analysis, we conclude that the charges always transfer from the Tb to Si atoms. Furthermore, from the magnetic properties analysis, we find that the magnetic moments are greatly increased after the doping of the Tb atom. The magnetic moment is largely located on Tb atom, and is mainly contributed by f-block electrons. The f electrons are much localized and to a large extent not responsible for chemical bonding. The partial density of states (PDOS) of TbSi10 shows that there is strong sp hybridization between Tb and Si atoms. The stable TbSi_n would be greatly used in magnetic materials in the near future.On the other hand, chooSi_ng the other transition metal atoms (Y, Pd, La, Yb, Lu) with different valence electron configuration as the doped atoms, we study the equilibrium geometries, electronic and magnetic properties of the TMSi_n clusters uSi_ng the density functional theory(DFT) within the generalized gradient approximation(GGA). The calculated results show that the TM atoms usually capped on the different surface sides of Si_n clusters at the size n<10. From n=11, the TM atoms gradually trapped into the Si_n clusters, especially for the Pd atom, trapped into the center earlier that at the size n=11. All the TM atoms form the cage structures at the size n=16. According to the calculated results about the magnetic properties, we find that the magnetic moments quenched completely at the size n=6. From the Mulliken populations, we find that the charge transfer direction always reversed as the clusters size increaSi_ng except the PdSi_n cluster. Besides, the hybridization mainly happens between sp-d orbits.
Keywords/Search Tags:Density functional theory(DFT), clusters, geometric structures, electronic properties, magnetic property
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