镁铝金属间化合物的第一性原理研究

First Principles Study on Mg-Al Intermetallic Compounds

采用基于密度泛函理论的第一性原理平面波赝势法,计算了Mg17Al12和Mg23Al30相的形成热、结合能、电子结构、热力学性质、弹性性质和熔点。形成热和结合能计算结果表明,Mg17Al12相的结合能和形成热较小,说明Mg23Al30相较容易生成且稳定;电子结构计算表明,Mg23Al30相结构稳定的原因是键合作用较强;弹性常数计算结果表明,Mg23Al30为塑性相,Mg17Al12为脆性相;热力学性质计算表明,室温以上温度范围内,Mg23Al30的Gibbs自由能最小,热结构相对稳定。采用经验公式预测得到Mg23Al30、Mg17Al12均为低熔点合金。

Planar wave pseudopotential method based on the first principle of density functional theory was employed to calculate the heats of formation,binding energy,electronic structures,thermodynamic properties,elastic properties and melting point of Mg17Al12 and Mg23Al30 phases.It could be found from the calculated results that Mg17Al12 phase showed smaller binding energy and heats of formation than Mg23Al30,indicating the easy generation and stability of Mg23Al30.The calculation results of electronic structures revealed that the stable structure of Mg23Al30 phase was derived from the strong bonding cooperation.Furthermore,it could be concluded that Mg23Al30 belonged to plastic phase and Mg17Al12 belonged to brittle phase according to elastic constant calculation results.The calculation of thermodynamic properties illustrated that Mg23Al30 possessed the smallest Gibbs free energyand a relatively stable thermal structure in the temperature range above room temperature.In addition,both Mg23Al30 and Mg17Al12 were predicted to be low melting point alloys by empirical formula.