Co@Au_n(n=1～8)团簇的几何结构和电子性质的理论研究

Theoretical study of geometrical structures and electronic properties for Co@Au_n(n=1～8) clusters

本文利用密度泛函PW91方法研究了Co@Au_n(n=1～8)团簇的平衡结构、稳定性和磁矩.结构优化显示Co原子在低能异构体中趋于占据最高配位位置,基态Co@Au_n(n=2～6)团簇为二维结构,Co@Au_7和Co@Au8转变为三维结构.原子平均结合能、二阶能量差分及HOMO-LUMO能级间隙分析表明掺杂Co原子提高了金团簇的稳定性,改变了金团簇能级间隙的奇偶振荡性,n=5为掺杂团簇的幻数.磁矩的计算揭示Co@Au_n团簇的磁性主要源于Co原子的3d轨道.

The equilibrium structures, stabilities and magnetic properties of Co@Aun （n= 18） clusters have been investigated using density functional theory at the PWgl level. The structural optimizations show that the Co atom in lowenergy isomers tends to occupy the most highly coordinated position. The groundstate Co@Aun clusters possess twodimensional structure for n= 26 and threedimensional structure for n=7 and 8. The relative stabilities of the groundstate Co@Au. structures are analyzed based on the averaged binding energies, secondorder difference of energies, and HOMOLUMO energy gaps. It is found that Co atom improves the stability of host cluster and the Co@Aus is magic cluster. The oddeven oscillation of energy gaps of gold clusters is changed by the Co atom. The magnetic mo ment calculations indicate that the total magnetic moment of Co@Au. clusters is mainly localized on the 3d orbital of Co atom.