5d过渡金属原子掺杂氮化硼纳米管的第一性原理计算

摘要

采用基于密度泛函理论的第一性原理计算方法,研究了当氮化硼纳米管(BNNT)中的B原子和N原子被5d过渡金属原子(Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg)取代时BNNT的几何结构、电子结构和磁性性质。作为对比,给出了理想BNNT, B缺陷体系(VB)和N缺陷体系(VN)的相应结果。研究发现：5d原子取代B(B5d)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；利用相同的5d原子进行掺杂时, B5d的成键能比N5d的成键能大；对于B5d或者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,取代B时体系的总磁矩呈现出较强的规律性。利用对称性和分子轨道理论解释了5d原子取代B时杂质能级的产生和磁性的变化规律。%The geometry, electronic structure and magnetic property of boron nitride nanotube (BNNT), whose boron/nitride atoms are substituted by 5d atoms (B5d or N5d), are investigated by first-principles calculations based on density functional theory. The pure-BNNT and BNNT with boron vacancy (VB) or nitrogen vacancy (VN) are also investigated for comparison. Results show that the local symmetry of B5d system is similar to C3v, however the N5d system exhibits a large geometric deviation from C3v. The total magnetic moments of doped systems are different from each other, and B5d system present a strong regularity. The total density of states is presented, where impurity energy levels exist. The impurity energy levels and total magnetic moment can be explained by the molecular orbital theory under C3v symmetry.