B2-YX(X=Cu,Rh,Ag,In)点缺陷结构及其基本物性的理论计算

Study on Point Defect Structures of B2-YX (X= Cu, Rh ,Ag, In) Intermetallic Compound and Their Basic Physics Properties

采用第一原理赝势平面波方法,计算了B2-YX(X=Cu,Rh,Ag,In)金属间化合物的基本物性。通过对不同点缺陷结构形成热和形成能的计算与比较,分析和预测了B2-YX金属间化合物中点缺陷结构的种类与存在形式。结果表明:B2-YX点缺陷结构主要是X子晶格上的空位与Y子晶格上的反位,在富Y的YX金属间化合物中主要为X空位,在富X的YX金属间化合物中则主要是X反位。通过对B2-YX金属间化合物完整晶体与点缺陷结构Cauchy压力参数C12-C44和G/B0值的比较,发现点缺陷能明显提高B2-YX金属间化合物的室温塑性,推测这很可能是含有点缺陷的实际B2-YX多晶材料比无缺陷理想单晶和NiAl多晶材料表现出更好室温塑性的原因之一。

Using a first-principles pseudopotential plane-wave method, energetics and several basic mechanical parameters of B2-YX （X=Cu, Rh, Ag, In） intermetallic compound and their point defect structures were calculated. The types and present forms of point defects in B2-YX intermetallic compound are analysed and forecasted in terms of the heat of formation and the formation energy. It is found that the major point defects in B2-YX intermetallic compound are the vacancy defect in the X sublattice or the anti-site defect in the Y sublattice, Le., X vacancy defect in rich-Y intermetallic compound and X anti-site defect in rich-X intcrmctallic compound. The comparison of Cauchy pressure parameter （C12-C44） and the G/Bo values of ideal B2-YX （X=Cu, Rh, Ag, In） crystals with their point defect structures reveals that these point defects are beneficial to improving the ductility of B2-YX intermetallic compound, which maybe is responsible for the outstanding ductility of B2-YX （X=Cu, Rh, Ag, In） intermetallic compound at room temperature compared with ideal B2-YXcrystals and the B2-NiAI multicrystal.