5d过渡金属原子掺杂氮化铝纳米管电子结构、磁性性质的第一性原理计算

Electronic and magnetic properties of 5d atoms doped aluminium nitride nanotubes: a first-principles calculation

采用基于密度泛函理论(DFT)的第一性原理计算方法,研究了5d过渡金属原子(Lu、Hf、Ta、W、Re、Os、Ir、Pt、Au、Hg)取代Al N纳米管(Al NNTs)中的铝原子或氮原子时体系的几何结构、电子结构和磁性性质;并且以理想Al N纳米管(Al NNTs)、Al缺陷体系(VAl)和N缺陷体系(VN)的结果作为对比.研究发现:5d原子取代Al(Al5d)时体系的局域对称性接近于C3v,但是取代N(N5d)时体系的局域对称性偏离C3v对称性较大;当掺杂的5d元素相同时,Al5d的成键能比N5d的成键能大;当掺杂体系相同时(Al5d或N5d),其成键能基本上随着5d原子的原子序数的增大而降低;掺杂体系中出现了明显的杂质能级,给出了态密度等结果;不同掺杂情况的磁矩不同,总磁矩呈现出较强的规律性.利用C3v对称性和分子轨道理论解释了过渡金属原子取代Al时杂质能级的产生和体系磁性的变化规律.

A first - principles calculation based on density functional theory is carried out to reveal the geometry, electronic structure and magnetic properties of aluminium nitride nanotubes （AlNNTs）, whose Al/N atoms are substituted by 5d atoms （A15d or N5d ）. The pure -AlNNTs and AlNNTs with Al vacancy （VAl） and N vacancy （ VN ） are also investigated for comparison. Results show that the local symmetry of A15a system is similar to C3v, while the N5d system exhibits a large geometric deviation from C3v. When AlNNTs are doped by the same 5d atom, the bonding energy of Al5d is higher than that of N5d ; when 5d atoms substitute for Al/N atoms, the bonding energy of system decreases along with the atomic number growth. There exist obvious impurity energy levels in the band gap, and the densities of states （DOSs） are presented. The total magnetic moment differs from each other when doped by different atoms, and the total magnetic moments of doped systems present a strong regularity. The impurity energy levels and total magnetic moments are explained by the molecular orbital theory under C3v local symmetry.