密度泛函理论研究ZrnCo(n=1-13)团簇的结构和磁性  

Density-functional study of Zr_n Co(n=1—13) cluster structers and their magnetism

作　　者：任凤竹[1] 王渊旭[1] 田付阳[1] 赵文杰[1] 罗有华[1] 

机构地区：[1]河南大学计算材料科学研究所物理与电子学院,开封475004

出　　处：《物理学报》2008年第4期2165-2173,共9页Acta Physica Sinica

摘　　要：利用密度泛函理论中的广义梯度近似对ZrnCo(n=1—13)团簇进行了结构优化、能量和频率的计算,研究了ZrnCo团簇的平衡几何结构、稳定性、电子性质和磁性.结果表明:Zr4Co,Zr7Co,Zr9Co和Zr12Co团簇的基态稳定性较高,是幻数团簇,尤其是Zr12Co团簇基态为Ih对称性的二十面体结构且稳定性特别高.ZrnCo团簇的磁矩随尺寸的变化可以分三个阶段:n=1—3有稳定的磁矩,从n=4开始磁矩出现振荡性的猝灭,直至n≥8磁矩完全猝灭.体系的磁矩主要来自局域d电子的贡献,ZrnCo团簇磁矩发生猝灭的主要原因是电荷转移和强烈的spd杂化效应.同时发现,过渡金属掺杂在不同特性材料中所形成的团簇体系,其结构、稳定性和磁性有些非常有意思的相似,如TMX12(TM代表过渡金属Fe或Co,X代表Si和Be)团簇、Zr13TM团簇.对此,值得进一步研究.The geometries, total energies, and frequencies of Zrn Co （ n = 1-13） clusters have been systematically investigated by using density functional theory with the generalized gradient approximation. The equilibrium geometries, stabilities, gap and magnetism have been determined. The results show that the relative stabilities of Zr4 Co, Zr7 Co, Zr9 Co and Zr12 Co are stronger than other sized clusters, indicating that they are magic number clusters, and especially, the true ground state for Zr12 Co cluster has icosahedral structure with 1h symmetry. Moreover, the stability of Zr12 Co is the strongest of all the investigated clusters. The magnetic moment of Zrn Co clusters mainly comes from the localized d electron. The system magnetic moment may be divided into three stages along with the size change ： n = 1-3 corresponds to the stable magnetic moment, the magnetic moment of Zrn Co clusters starts to show vibration quenching from n = 4, until n = 8 when the magnetic moments is completely quenched. The charge transfer and the strong hybridization between s, p and d states might be one major reason for quenching of the magnetic moment of Zrn Co clusters. Meanwhile, the clusters which are composed of transition metals doped in different characteristic materials is worth further studying, for example, TMX12 and Zr13TM clusters have interestingly similar structures, stability and magnetism.

关 键 词：ZrnCo团簇 平衡几何结构 稳定性和磁性 

分 类 号：O561[理学—原子与分子物理] O481[理学—物理]