Structural, Electronic And Magnetic Properties Of Cu_n+1 And M@Cu_n （n=1-12, M=Sc-Ni） Clusters:Density Functional Theory Study

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.