基于第一性原理L12-Al 3 Sc点缺陷结构及成键行为的计算

摘要

运用第一性原理平面波赝势方法计算金属间化合物L12-Al 3 Sc的基本物性，并通过计算点缺陷形成能推测L12-Al 3 Sc点缺陷的主要存在形式，结合电荷密度和态密度的分析揭示L12-Al 3 Sc的成键行为。结果表明：L12-Al 3 Sc的晶格常数为4.107Å，体模量为86.5 GPa，形成焓为−43.83 kJ/mol。L12-Al 3 Sc的点缺陷主要为Al亚晶格上的Al空位和Sc反位缺陷。L12-Al 3 Sc中Sc空位与Al反位缺陷的形成能较为接近，表明富Al合金中Sc空位和Al反位缺陷易于共同存在；Sc反位缺陷的形成能小于Al空位的，表明富Sc合金的点缺陷为Sc反位缺陷。L12-Al 3 Sc的成键电荷密度呈纺锤状，表现出Sc d-Al p的轨道杂化效应，其杂化轨道主要为Sc dz2-Al pz轨道杂化。%The first-principles pseudopotential plane-wave calculation was used to study the energies and the electronic properties of point defects for L1 2-Al 3 Sc intermetallic. According to the calculation and comparison of the formation energy of point defect structures, the geometrical configuration of point defects in L1 2-Al 3 Sc intermetallic was analyzed. Combining with densities of states and charge densities, the effect of bonding behavior on electronic structure was investigated emphatically. The results show that the lattice constant of L12-Al3Sc is 4.107 Å,bulk modulus is 86.5 GPa, and formation enthalpy is−43.83 kJ/mol. These calculation results also suggest that the point defects in the Al sublattices, i.e., Al vacancy and Sc anti-site, are more favorable than those in the Sc sublattices for the stoichiometric compound Al3Sc in the L12 structure, but Sc vacancy and Al anti-site defect coexist in rich-Al alloy, and mainly Sc anti-site defect can be found in rich-Sc alloy. The Al vacancy-induced charge density shows the spindle-like bonding characteristic, and Sc dz2-Al pz orbital hybridization is depicted.