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A Theoretical Study on Geometries and Electronic Structure of Gold Clusters

Author: DengXiaoHui
Tutor: LiPing
School: Sichuan University
Course: Atomic and Molecular Physics
Keywords: Au cluster Geometric and electronic structure First-principles Density Functional
CLC: O562
Type: Master's thesis
Year: 2007
Downloads: 203
Quote: 1
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Abstract


Transition metal atom clusters due to its peculiar physical and chemical properties has been in the field of material physics, nanotechnology, microelectronics, physical chemistry, and biological sciences has been widely used. With the rapid development of the birth of the density functional theory and computer hardware, the atomic clusters geometry and electronic structure of the first principles calculations possible. Gold element has a very large relativistic effects, due to its unique physical and chemical properties, and applications in catalysis, gold clusters is to become the most popular of the experimental and theoretical studies. In order to explore the gold clusters strange physical and chemical properties of the microscopic mechanism, using first-principles methods based on density functional theory study Au_n (2 ≤ n ≤ 10) Clusters geometry and electronic structure. First, using GAUSSIAN03 program the B3LYP function, select double (?) Effective core potential LANL2DZ search of the ground state structure, at the same time on the stability of the geometry and electronic structure are analyzed. The calculation results show that the gold clusters ground state Au_n (2 ≤ n ≤ 10) are planar structures. Binding energy and its second-order difference Fermi level, the study found that the energy gap in the presence of significant gold clusters parity resonance effect, which agrees well with the experimental data and other theoretical calculation. Based on the structure of the ground state calculation of the effective core potential, we further use DMOL program all-electron scalar relativistic calculations to obtain a more accurate parameters of the ground state of the gold clusters and electronic structure. For comparison purposes, the use of both BLYP and PBE exchange-correlation function. Meanwhile, gold clusters after the introduction of full electronic consider changes in the binding energy, the second-order difference Fermi level and the energy gap are discussed in detail. Calculation found that the addition of all-electronic considerations, the average bond length contraction of 3% -5%, and the average binding energy increases by 3% -5% Fermi level increases of 11% -15%, the energy gap larger changes reached about 50%, while the binding energy of the second-order differential because it is an average effect, little change. This study shows that the application relativistic effective core potential and all-electron scalar relativistic study geometric configuration and electronic structures of gold clusters can get consistent results. Au_n (2 ≤ n ≤ 10) clusters are planar ground state configuration. Binding energy, the second-order difference Fermi level and the energy gap exhibit parity resonance effects, which can be explained by electron pairing: even clusters of gold atoms have an even number of valence electrons, even number of valence electrons just two two pairing arrangement in the corresponding molecular orbital, a spin-up, one down, its relatively closed electron shells, and therefore more stable. An odd number of atoms of gold clusters, there is a single unpaired electron, and therefore relatively active.

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