M_2Sn_(17)(M=Ni,Mn)及其阴离子的几何结构、电子结构和磁性的计算研究

Geometric structures, electronic properties, and magnetism of M_2Sn_(17)(M=Ni,Mn)and their anions

采用密度泛函理论(density functional theory,DFT)中的广义梯度近似(generalized gradient approximation,GGA)对Ni2Sn17,Mn2Sn17,[Ni2Sn17]4-和[Mn2Sn17]2-三种同分异构体的几何结构、电子结构和磁性进行了研究.发现:在三种同分异构体中,D2d结构的Ni2Sn17,Mn2Sn17,[Ni2Sn17]4-和[Mn2Sn17]2-最为稳定.磁性研究表明:中性团簇Ni2Sn17的D2d结构和D4d结构出现了自旋分裂能级,分别带有4μB和2μB的磁矩.其中,Ni原子与Sn原子之间存在弱的铁磁相互作用.而D4h结构磁矩为零.另一方面,对于中性团簇Mn2Sn17,三种结构都有磁矩,大小分别是2μB,6μB和2μB.其中,Mn原子与Sn原子之间,D2d结构存在弱的反铁磁相互作用而D4h结构主要是弱的铁磁相互作用.D4d结构中的Mn与Sn之间既有弱的铁磁又有弱的反铁磁相互作用.对于两种团簇的负离子[Ni2Sn17]4-和[Mn2Sn17]2-,三种结构都是闭壳层结构,体现为非磁性.

The geometric structures and magnetism of the three probable isomers for Ni2Sn 17 ,Mn2Sn 17 ,[Ni2Sn 17 ]^ 4- and [Mn2Sn 17 ]^ 2- have been studied using the generalized gradient approximation based on density functional theory. It was found that the D 2d structures of Ni2Sn 17 ,Mn2Sn 17 ,[Ni2Sn 17 ]^ 4- and [Mn2Sn 17 ]^ 2- are the most stable structures among the three possible isomers. The study shows that the D 2d structure and the D 4d structure of Ni2Sn 17 have spin-splitting, leading to the magnetic moment 4μB and 2μB, respectively, and there is weak ferromagnetic interaction between the Ni and Sn atoms for the D 2d structure and the D 4d structure. However, there is no magnetic moment in the D 4h structure. On the other hand, the D 2d , D 4d , and D 4h Mn2Sn 17 have 2μB,6μB and 2μB magnetic moments, respectively. It is interesting that there is weak antiferromagnetic interaction and weak ferromagnetic interaction between Mn and Sn atoms for the D 2d and D 4h structures, respectively, while there is not only weak ferromagnetic interaction but also weak antiferromagnetic interaction between Mn and Sn atoms in the D 4d structure. Finally, It is worth noting that all their anion counterparts of [Ni2Sn 17 ]^ 4- and [Mn2Sn 17 ]^ 2- have closed electronic configurations, showing no magnetic moment.