科研之友
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摘要
The all-electron spin-polarized generalized gradient approximation to the density-functional theory is used to determine the binding energies, ground-state structures, electronic structures, and magnetic properties of the Y-n clusters (n <= 17). The structural evolution of yttrium clusters, which favors a compact and icosahedral structural growth pattern, is elucidated and compared with the other group-III elemental clusters. The results show that clusters with n=7,13 are more stable than their respective neighbors. Furthermore, the maxima of magnetism at n=8 and n=13 observed experimentally are well described and the magnetic moments for most yttrium clusters are quite small except for Y-6, Y-8, and Y-12-Y-14. Particularly, the regular icosahedron structure with a giant moment of 19 mu(B) is favored for the Y-13 cluster. The similar magnetic features of the scandium and yttrium clusters shown in experiments can be attributed to a common structural motif for these two series of clusters. A change of magnetic ordering from ferromagnetic to antiferromagnetic is observed at n=7, the exception being the systems Y-n with n=8,13,14 which are found to be ferromagnetic. In addition, the calculated ionization potentials are in good agreement with the experimental results, which imply that the predictions of the ground-state geometries of those clusters are accurate.
