摘要
采用基于密度泛函理论的第一性原理赝势平面波方法,计算了Mg-Al-Si-Ca合金系金属间化合物Mg2Si,Mg2Ca,Al2Ca以及Si2Ca四相的形成焓,结合能,弹性常数及态密度。形成焓和结合能的计算结果表明:Al2Ca的合金化能力最强,Si2Ca相的结构最稳定;体模量(B)、剪切模量(G)、杨氏模量(E)和泊松比(ν)的计算结果表明:四相均为脆性相,且Mg2Si相的塑性最差,结合弹性模量和态密度分析,得出Mg2Ca的塑性最好;态密度和Mulliken布居分析表明:四相中均存在离子键和共价键,共价键由强到弱顺序为Si2Ca,Al2Ca,Mg2Si,Mg2Ca;而离子键强弱顺序按Mg2Si,Al2Ca,Si2Ca,Mg2Ca依次递减;而Si2Ca最稳定的原因是其共价键比其他三相更强。
Structural stabilities, mechanical properties and electronic structures of Mg2Si, Mg2Ca, Al2Ca and Si2Ca in Mg-AI-Si-Ca alloy have been determined from first-principles calculations by CASTEP program based on the density functional theory. The calculated formation enthalpy and cohesive energies show that A12Ca has the strongest alloying ability and Si2Ca possesses the highest structural stability. The calculated bulk moduli （B）, Young＇s moduli （E）, shear moduli （G） and Poisson ratio （v） indicate that the four phases are brittle and among them Mg2Si is a phase with the worst brittleness. Then based on elastic modulus and DOS, we reveal that Mg2Ca has the best plasticity. The calculations of the density of states （DOS） and Mulliken electronic populations suggest that the four phases are all have ionic bonds and covalent bonds. The strength of the covalent bond order is Si2Ca〉AlECa〉MgESi〉MgECa; while the strength of the ionic bond order is Mg2Si〉A12Ca〉Si2Ca〉Mg2Ca. And Si2Ca is more stable than others because it has the strongest covalent bonds.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2014年第11期2733-2738,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)
关键词
第一性原理
镁合金
金属间化合物
电子结构
弹性常数
first principles
magnesium alloy
intermetallics
electronic structure
elastic constants
