【作者】 王玲；

【导师】 迭东；

【作者基本信息】 西华大学 ， 凝聚态物理， 2015， 硕士

【摘要】 铜具有导电性好、延展性佳、储量丰富及加工方便等优点,还具有极强的抗癌、抑菌功能,已被广泛应用于电气、机械、轻工、建筑、国防和医学等领域。铜团簇作为介于单个Cu原子到块状铜的过渡态,其物理和化学性质既不同于单个的原子,又有别于块状的铜,一般随原子数目的变化而改变。近年来,为优化铜团簇的结构和物性,铜团簇掺入Au、Ag已被广泛地研究,但对于铜团簇掺入3d过渡金属的研究却甚少。因此,本文拟对Cun+1和M@Cun(n=1-12,M=Sc-Ni)团簇的几何结构、相对稳定性和磁性能进行系统地研究。首先,基于密度泛函理论B3LYP方法,优化了Cun+1和M@Cun(n=1-12,M=Sc.Ni)团簇的几何结构,得到许多异构体。几何结构优化结果显示Cun+1团簇的基态结构随着Cu原子个数的增加趋向于笼状结构,Cun+1团簇的基态结构在n=2-5为平面结构,在n=6-12为三维结构；对于掺杂M@Cun团簇,所有过渡金属原子在基态结构中明显趋于占据高配位。其次,原子平均结合能的计算结果表明：随着铜原子的增加,铜团簇和掺杂团簇的原子平均结合能呈增大趋势；掺杂团簇(除Cr@Cun和Mn@Cun团簇外)的原子平均结合能明显大于纯铜团簇。对于基态团簇的能量二阶差分,Cun+1、M@Cun(M=Cr、Co、 Ni)表现出明显的奇偶振荡特性,即含偶数Cu原子团簇的稳定性高于含奇数Cu原子团簇的稳定性。对于垂直电离能(VIP)和电子亲和能(EA),Cun+1、Co@Cun、Ni@Cun的VIP和EA均具有奇偶振荡特性,具有相同自旋多重性的M@Cun(M=Ti、Cr、Mn、Fe. Co、Ni)的EA随着团簇的增大而增大。对能级间隙的分析表明：除Ni@Cu3、Ni@Cu9、 Co@Cu11、Ni@Cu11外,过渡金属原子掺入到奇数铜原子团簇中,与相同数目原子的纯铜团簇相比,它们降低了铜团簇的能级间隙；相反,除Cr@Cu2外,其他掺杂原子掺入到偶数铜原子团簇中,与相同数目原子的纯铜团簇相比,它们增加了铜团簇的能级间隙。最后,基态团簇的总磁矩和轨道磁矩结果显示：掺杂原子Cr和Mn对铜团簇磁矩的影响最大,其中,Sc@Cun、Co@Cun、Ni@Cun的磁矩呈奇偶振荡现象。纯铜团簇和掺杂团簇的自旋态密度的分析表明：掺杂团簇改变了铜团簇的自旋态密度。对轨道磁矩研究分析表明：掺杂铜团簇的磁矩主要源于掺入的过渡金属原子,而过渡金属原子的磁矩又主要分布在它们的3d轨道上。更多还原

【Abstract】 Copper has advantages of good electrical conductivity, ductility, possessing abundant and processing convenience. Meanwhile, copper also has the function of anti-cancer and antifungal/antibacterial. So, copper has been extensively applied in the fields of electricity, machinery, light industry, architecture, national defense and medicine. Cu clusters, as the transition state between single Cu atom and lump copper, are not only different with single Cu atom in physicochemical properties, but also have distinctions with lump copper. The physicochemical properties of Cu cluster will change with increasing the amount of Cu atoms. Recently, in order to optimize the structure and properties of Cu clusters, Au/Ag-doping in copper clusters have been wildly researched. However, the work on 3d transition metal doping in copper clusters have not been reported so much. Therefore, the geometrical structure, electronic and magnetic properties of small Cun+i and M@Cun (n=1-12, M=Sc-Ni) clusters are investigated systematically in this paper.Firstly, geometry optimizations of the Cun and M@Cun (n=1-12, M= Sc-Ni) clusters are performed using DFT with the B3LYP change-correlation functional and many isomers have been obtained. The results show that Cu clusters tends to form a cage with the increasing number of Cu. The M (M=Sc-Ni) atom in the ground state M@Cun (n=1-12) clusters, which possess a planar structure for n=3-6 and a 3D structure for n=7-12, possibly occupy the most highly coordinated position.Secondly, it is found from the atomic averaged binding energies that it is a monotonically increasing function of the Cun+i and M@Cun clusters. Except for the doping of the Cr and the Mn, other doped clusters are bigger than that of the Cun+i cluster in the atomic averaged binding energies. The second-order energy differences of the Cun+i and M@Cun (M= Cr, Co, Ni) exhibit that ground-state clusters with even n are more stable than ground-state clusters with odd n, which imply those clusters own an odd-even oscillation. Meanwhile, the most stable Cun+1, Ni@Cun, and Co@Cun clusters also show an odd-even oscillation in vertical ionization potential and electron affinity (EA). In the same spin state, the EA of M@Cun (M= Ti, Cr, Mn, Fe, Co, and Ni) clusters increases while cluster size increase. The analysis of energy gap indicates the dopant of M atom in M@Cun (M= Sc-Ni) clusters, which do not include Ni@Cu3, Ni@Cu9, Co@Cun, Ni@Cun and Cr@Cu2, in odd-numbered Cun clusters, the HOMO-LUMO energy gap decrease, whereas the HOMO-LUMO gap increase in even-numbered Cun clusters.Thirdly, the magnetic moment of the most stable clusters are calculated. The Cr and Mn atoms doped in Cun clusters can markedly enhance the magnetic moment of host clusters. The Sc@Cun, Co@Cun, Ni@Cun clusters show an odd-even alternation with the number of Cu atoms in total magnetic moment. Simultaneously, the doped clusters significantly change the spin density of state. The local magnetism investigations indicate that the total magnetism moment of M@Cun clusters is chiefly derived from 3d orbital of M atom.更多还原