CoAlN(N=2-11)团簇基态结构的稳定性和磁性

采用密度泛函理论中的广义梯度近似(GGA),对CoAlN(N=2-11)团簇进行构型优化和磁性计算.在考虑自旋多重度的情况下得到了团簇的平衡构型及基态结构,并重点讨论了Co原子的sp-d杂化效应对体系稳定性和磁性的影响.结果表明:N为偶数时,团簇的基态为自旋双重态,Co原子磁矩随N增加整体上呈减小趋势;N为奇数时(除N=5为自旋三重态外),团簇的基态为自旋单重态,Co原子磁矩为零.N≥8时,Co原子陷入主团簇内部,体系的对称性降低,稳定性增强;轨道杂化增强了体系的稳定性,但减小了双重态和三重态体系中Co原子的磁矩;N=3,8,10是团簇CoAlN(N=2.11)的幻数.

Stablities and Magnetism of the ground-state structures of CoAlN(N=2-11)Clusters

The geometry structures of CoAlN(N=2-11)clusters have been optimized,and the magnetic moment of Co atom of CoAlN(N=2-11)clusters have been investigated by using generalized gradient approximation of density functional theory.The equilibrium geometries with different spin multiplicity as well as the ground states structures were obtained .Also,more emphysises have been placed on the effects of the sp-d hybridization of Co atom on the stabilities and magnetism.The results indicate: when the number of N is even, the spin multiplicity is doublet in which the magnetic moment of Co atom reduce continouely while it is singlet (except the CoAl5 is triplet ) as the number of N is odd where the magnetic moment of Co atom is quenched. The Co atom falls into the interior site of the host cluster from N=8,which results in the lower symmetries and the enhancement of stabilities of the clusters. The sp-d hybridization of Co atom enhences the stabilities of the CoAlN(N=2-11)clusters but reduces the magnetic moment of Co atom of the CoAlN clusters with doublet and triplet multiplicity. N=3,8,10 is the magic number of the CoAlN(N=2-11)clusters.