压力下Mg_(2)Ca、Al_(2)Ca和Mg_(2)Si相稳定性的第一性原理研究

First-principles Study on Phase Stability of Mg_(2)Ca,Al_(2) Ca and Mg_(2)Si under Pressure

采用第一性原理的计算方法优化了施加0~50 GPa静水压力下Mg_(2)Ca、Al_(2)Ca和Mg_(2)Si相的晶胞结构,并计算了不同静水压力下Mg_(2)Ca、Al_(2)Ca和Mg_(2)Si相的弹性性能和电子结构,以此来研究静水压力对各相结构稳定性、弹性性能和电子结构的影响。结果表明:Mg_(2)Ca、Al_(2)Ca和Mg_(2)Si相的晶格常数随施加压力的增大而逐渐减小,并且降低的速率呈逐渐缓慢的趋势;逐渐施加静水压力后,Mg_(2)Ca、Al_(2)Ca和Mg_(2)Si相的体模量、剪切模量、杨氏模量、泊松比以及体模量/剪切模量的值均呈现了不同程度的增长态势,表明施加适当的静水压力可提高Mg_(2)Ca,Al_(2)Ca和Mg_(2)Si相的塑性和延展性,进而改善镁合金的力学性能。随着压力的增加,各相的结构没有发生相变,并且Mg_(2)Si的结构在静水压力下显现出稳定性最强的特性,Al_(2)Ca次之,Mg_(2)Ca相的稳定性在静水压力下逐渐变差。

By using first-principles calculation methods,the unit cell structure of Mg_(2)Ca,Al_(2)Ca and Mg_(2)Si phases under hydrostatic pressure of 0-50 GPa was optimized.The elastic properties and electronic structure of Mg_(2)Ca,Al_(2)Ca and Mg 2 Si phases under different hydrostatic pressures were calculated.The influence of hydrostatic pressure on the stability of each phase structure,elastic properties and electronic structure were studied.The results show that the lattice constants of Mg_(2)Ca,Al_(2)Ca and Mg_(2)Si phases gradually decrease with the increase of applied pressure,and the rates of decrease show a gradually slow trend.After the hydrostatic pressure is gradually applied,the bulk modulus,shear modulus,Young's modulus,Poisson's ratio and bulk modulus/shear modulus of Mg_(2)Ca,Al_(2)Ca and Mg_(2)Si phases all show different degrees of growth.It shows that applying proper hydrostatic pressure can increase the plasticity and ductility of Mg_(2)Ca,Al_(2)Ca and Mg_(2)Si phases,thereby improving the mechanical properties of magnesium alloys.With the increase in pressure,the structure of each phase does not change,and the structure of Mg_(2)Si shows the strongest stability under hydrostatic pressure,followed by Al_(2)Ca,and the stability of Mg_(2)Ca gradually deteriorates under hydrostatic pressure.