笼状Au_(20)内掺M_(13)(M=Fe,Ti)团簇磁性的密度泛函计算研究

The magnetism of M_(13)-doped cagelike structure of gold clusters(M=Fe,Ti):density functional calculations

采用密度泛函理论中的广义梯度近似方法,对M13(M=Fe,Ti)以及M13内掺Au20团簇的几何结构和磁性进行了计算研究.结果表明:M13和M13内掺Au20团簇的几何结构在0.006—0.05nm误差范围内保持着Ih对称性.Fe13团簇最低能态的总磁矩为44μB,内掺到Au20笼中后形成的Fe13内掺Au20团簇的最低能态总磁矩为38μB,且Au原子与内掺Fe13团簇之间存在着弱铁磁相互作用.Ti13团簇在总磁矩为6μB时能量最低,掺入Au20笼后形成的Ti13内掺Au20团簇最低能态总磁矩是4μB,内表面12个Ti原子与表面Au壳之间是弱铁磁相互作用,而与中心Ti原子之间是弱反铁磁相互作用.由于Au20笼状外壳的影响,Fe13内掺Au20和Ti13内掺Au20团簇中Fe13和Ti13的磁矩比无金壳的Fe13和Ti13团簇的磁矩分别减少了6.81μB和2.88μB.

The geometric and magnetic properties of M13 and Mla-doped Au20 （M = Fe, Ti） clusters have been studied using the generalized gradient approximation based on the density functional theory. The optimized geometries of the clusters are close to the Ih structure within 0.006--0.05 nm tolerance. The lowest-energy spin states of the Fel3 and Fela-doped Au20 clusters are 44 μB and 38μB, respectively, while there is week ferromagnetic interaction between the Fe and Au atoms for the Fe13-doped Au20 cluster. On the other hand, the lowest energy spin states of the Til3 and Ti13-doped Au20 clusters are 6 μB and 4 μB, respectively. The magnetic ordering is in a week ferromagnetic arrangement between the 12 surface Ti atoms and Au atoms, while in a week antiferromagnetic arrangement between the 12 surface Ti atoms and the core Ti atom. Comparing with the bare Fel3 and Ti13 clusters, the magnetic moments of Fel3 and Ti13 in Fe13-doped Au20 and Til3-doped Au20 clusters are reduced by 6.81μB and 2.88μB, respectively.