Ca、Sr和Ba掺杂Mg_2Si弹性性能和电子结构的第一性原理研究  

First-Principles Study on Elastic Properties and Electronic Structure of Ca, Sr and Ba Doped Mg_2Si

作　　者：赵慧[1] 赵宇宏[1] 杨晓敏[1] 眭怀明 侯华[1] 韩培德[3] 

机构地区：[1]中北大学,山西太原030051 [2]扬州峰明金属制品有限公司,江苏扬州225117 [3]太原理工大学,山西太原030024

出　　处：《稀有金属材料与工程》2015年第3期638-643,共6页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51204147;51274175;50975263);科技部国际科技合作项目(2011DFA50520);山西省回国留学人员科研项目(2011-重点6)

摘　　要：采用第一性原理平面波赝势方法研究了合金元素X(X=Ca、Sr、Ba)掺杂Mg2Si的占位情况:(1)取代Mg原子位置;(2)取代Si原子位置;(3)间隙固溶到Mg2Si晶胞中。分析合金系Mg7Si4X,Mg8Si3X,Mg8Si4X的形成热和结合能可知,Mg7Si4X的形成热和结合能均为负值,且最小。表明Mg7Si4X更容易形成稳定化合物,具有较强的合金化能力,且Ca,Sr,Ba掺杂Mg2Si时有优先占据Mg原子的倾向。研究Mg7Si4X的弹性模量和电子结构发现:Mg7Si4Ca、Mg7Si4Sr为脆性相;Mg7Si4Ba为延性相,塑性最好;掺杂Ca,Sr,Ba使Mg2Si逐渐由脆性向韧性转变。Ca,Sr,Ba的掺入均使Mg2Si的电子态密度发生偏移,费米能级处的电荷密度增加,导电性增强,共价键作用减弱,合金系结构稳定性减弱。Using the first-principles plane-wave pseudopotential method, the placeholder positions of the alloying element X（X = Ca, Sr, Ba）doped Mg2 Si were investigated, including substitutional elements of Mg site, substitutional elements of Si site and being inserted into Mg2 Si unit cell. The enthalpy of formation and the binding energy of Mg7Si4 X are both negative and minimum shown from the calculated results of Mg7Si4 X,Mg8Si3X and Mg8Si4X（X = Ca, Sr, Ba）, which demonstrate that Mg7Si4 X is easier to form a stable compound with the strong alloying capability.Therefore X atom is more favorable to occupy the Mg position comparing with other sites. The elastic modules and electronic structures of Mg7Si4 X show that Mg7Si4 Ca and Mg7Si4 Sr are brittle phases. Mg7Si4 Ba is a ductile phase with the best plasticity. The doped elements make Mg2 Si transit from brittle to ductile gradually. The electronic density of states has a shift with Ca, Sr and Ba doping, the charge density on Fermi level increases and the electrical conductivity increases. Besides, the covalent bond and the structural stability of the systems are weakened.

关 键 词：MG2SI 第一性原理 弹性性能 电子结构 

分 类 号：TB34[一般工业技术—材料科学与工程]