基于第一性原理的D8m-Mo5Si3成键特征与点缺陷行为

来源期刊:中国有色金属学报2020年第11期

论文作者:顾顺 王斌 孙顺平 李小平 江勇 易丹青

文章页码:2526 - 2540

关键词:D8m-Mo5Si3;点缺陷;成键特征;结构稳定性;第一性原理计算

Key words:D8m-Mo5Si3; point defect; bonding characteristic; structural stability; first principles calculation

摘    要:运用第一性原理平面波赝势方法,对D8m-Mo5Si3化合物的空位与反位缺陷的形成能、点缺陷浓度及其电子结构进行计算,研究D8m-Mo5Si3的成键行为,并分析了其点缺陷结构的稳定性。结果表明:D8m-Mo5Si3的晶格常数a=9.6808 ?,c=4.9033 ?,体模量B0=247.08 GPa。Mo5Si3的成键电荷密度呈现出纺锤状特征,表明了Mo 4d态和Si 3p态之间的局部杂化效应。由形成能的计算结果可知,在富Mo合金中MoSi1缺陷最稳定,在富Si合金中SiMo2缺陷最稳定。究其原因是因为在MoSi1和SiMo2这两种缺陷中Si和Mo原子之间的电荷积累效应得到增强,相互作用增大。结合Wagner-Schottky模型,研究了在2173 K下D8m-Mo5Si3的点缺陷浓度与成分之间的关系,计算结果再次证实了MoSi1和SiMo2是富Mo或富Si合金中最主要的缺陷形式。

Abstract: The formation energies, point defect concentrations and electronic structures of point defects for D8m-Mo5Si3 were calculated by the first-principles pseudopotential plane-wave method. Furthermore, the effect of bonding behaviors and structural stability were investigated emphatically. The results show that lattice constants of Mo5Si3 are 9.6808 ? and 4.9033 ?, and the bulk modulus is 247.08 GPa. The Mo vacancy-induced charge density shows the spindle-like bonding characteristic, and the localized hybridization focuses on Mo 4d state and Si 3p state. From the formation energies, MoSi1 and SiMo2 are the most stable defect structures in Mo-rich and Si-rich alloys, respectively. It is because the larger charge accumulation between Mo and Si strengthens the interaction for MoSi1 and SiMo2 anti-site defects. Combining with Wagner-Schottky model, the point defect concentrations at 2173 K as a function of composition were also investigated, and the results show that MoSi1 and SiMo2 are the main defect forms of Mo-rich and Si-rich alloys, respectively.

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