(1. 江蘇理工學院 江蘇省先進材料設計與增材制造重點實驗室，常州 213001；
2. 中南大學 材料科學與工程學院，長沙 410083)
摘 要: 運用第一性原理平面波贗勢方法，對D8m-Mo5Si3化合物的空位與反位缺陷的形成能、點缺陷濃度及其電子結構進行計算，研究D8m-Mo5Si3的成鍵行為，并分析了其點缺陷結構的穩(wěn)定性。結果表明：D8m-Mo5Si3的晶格常數(shù)a=9.6808 ？，c=4.9033 ？，體模量B0=247.08 GPa。Mo5Si3的成鍵電荷密度呈現(xiàn)出紡錘狀特征，表明了Mo 4d態(tài)和Si 3p態(tài)之間的局部雜化效應。由形成能的計算結果可知，在富Mo合金中MoSi1缺陷最穩(wěn)定，在富Si合金中SiMo2缺陷最穩(wěn)定。究其原因是因為在MoSi1和SiMo2這兩種缺陷中Si和Mo原子之間的電荷積累效應得到增強，相互作用增大。結合Wagner-Schottky模型，研究了在2173 K下D8m-Mo5Si3的點缺陷濃度與成分之間的關系，計算結果再次證實了MoSi1和SiMo2是富Mo或富Si合金中最主要的缺陷形式。
關鍵字: D8m-Mo5Si3；點缺陷；成鍵特征；結構穩(wěn)定性；第一性原理計算
（1. Jiangsu Key Laboratory of Advanced Materials Design and Additive Manufacturing, Jiangsu University of Technology, Changzhou 213001, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
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.
Key words: D8m-Mo5Si3; point defect; bonding characteristic; structural stability; first principles calculation
