Mg24Y5和MgCu2中点缺陷的理论究-化学工艺专业毕业论文.docx

电子因素也很强烈，这些尺寸因素和电子因素对点缺陷的形成和结果 电子因素也很强烈，这些尺寸因素和电子因素对点缺陷的形成和结果 有着明显影响。 2、采用第一性原理计算研究了C15 Laves相MgCu2中的点缺陷。 点缺陷形成能和缺陷化合物的形成能都表明C15 MgCu2中主要缺陷 结构分别是在富Mg下的Mgcu反位缺陷和富Cu下的CuMg反位缺陷。 通过巨正则统计模型获得了缺陷浓度随MgCu2组分变化的函数曲线。 进一步计算了缺陷附近的局域几何变化并揭示了原子尺寸因素的影 响。电子态密度和电荷分布表明从Mgcu到Vcu体系及从CuMg IJ VMg 体系的稳定性逐渐变弱。止P3l-，还研究了含缺陷的MgCu2体系中盈 的掺杂，我们发现，相对于Mg晶格，Zn在Cu晶格形成焓更低因而 有更强的掺杂趋势。电子结构进一步研究表明，含有Zn原子掺杂体 系的稳定性源于Cu—Cu和Zn—Cu较强的共价键。 关键词：镁合金 点缺陷 第一性原理计算形成能原子尺寸效应 电子结构原子掺杂 万方数据 THEORETICAL THEORETICAL STUDY OF POINT DEFECTS IN M924Y5 AND MgCu2 ABSTRACT As excellent light-weight structural materials，Mg alloys have advantages such as low density,high speci fic strength and speci fic stiffness．Therefore，Mg alloys have been widely applied．Point defects strongly affect the structure and properties of materials，SO limit to some extent for the property and application of Mg alloy materials．The experimental identification of defect is typically difficult and indirect， therefore theoretical investigations of defects are very necessary． First-principles calculations have emerged as a powerful approach that complements experiments and can serve as a predictive tool in the identification and characterization of defects for Mg alloys．Therefore， First-principles calculations with GGA approximation are performed to study the point defects in M924Y5 and MgCu2．The main investigations are as following： Firstly,eight possible native point defects in M＆4Y5 are studied from the density functional theory(DFT)calculations．The energetic results show that antisite defects with lower formation energies are energetically favored over vacancies．Under both Mg-rich and Y-rich III 万方数据 conditions，Mgvl conditions，Mgvl defect is dominant due to the lowest defect formation energy,followed by YM92，Mgv2 and YM91，which reasonably explains the Mg—rich off-stoichiometry of M924Y5 alloys．For vacancy defects，the formation energies on the two Mg sublattices are smaller than ones on two Y sublattices，and VM91 has the lowest fo