压力作用下Mg_2X(X=Si,Ge)相热力学性质的第一性原理研究  

Thermodynamic Properties of Mg_2X(X=Si,Ge)Phases under Pressure by First-Principles Calculations

作　　者：张乐婷[1] 赵宇宏[1] 孙远洋[1] 邓世杰[1] 吉如意 韩培德[2] ZHANG Leting;ZHAO Yuhong;SUN Yuanyang;DENG Shijie;JI Ruyi;HAN Peide(College of Materials Science and Engineering,North University of China, Taiyuan 030051 , China;College of Materials Science and Engineering,Taiyuan University of Technology,Taijuan 030024, China)

机构地区：[1]中北大学材料科学与工程学院,山西太原030051 [2]太原理工大学材料科学与工程学院,山西太原030024

出　　处：《高压物理学报》2018年第3期8-15,共8页Chinese Journal of High Pressure Physics

基　　金：国家自然科学基金(51774254;51774253;51701187;U1610123;51674226;51574207;51574206);山西省科技重大专项(MC2016-06)

摘　　要：采用基于密度泛函理论的第一性原理方法,研究了压力作用下Mg_2Si和Mg_2Ge的结构、弹性和热力学性质。计算结果表明:0GPa压力作用下两者的晶格参数与实验值以及其他理论值吻合较好,且相对晶格常数a/a_0和晶胞体积V/V_0均随压力的增大而减小;在0~25GPa压力作用下,Mg_2Si和Mg_2Ge相体模量B、剪切模量G、杨氏模量E均随压力的增大而增大,材料的刚度和塑性均增强,当压力达到15GPa时,材料由脆性转变为延性。最后借助准谐德拜模型和Gibbs软件,研究了温度与压力对Mg_2Si和Mg_2Ge的德拜温度、体模量、热容和热膨胀系数的影响。The structural,elastic and thermodynamic properties of Mg2Si and Mg2Ge phases under pressure were calculated using the first-principles based on the density functional.The calculated results indicated that the lattice parameters under 0 GPa are fairly consistent with the experimental value and other theoretical data.The ratio of a/a0 and V/V0 decreased as the external pressure increases.An appropriate pressure（0-25 GPa）can improve their stiffness and plasticity because the bulk modulus B,shear modulus G,and Young’s modulus Ealmost linearly increase with pressure.The brittleness of the material turns to ductility at 15 GPa.Finally,the effect of temperature and pressure on the Debye temperature,bulk modulus,heat capacity and linear thermal expansion coefficient was studied using the quasi-harmonic Debye model and Gibbs software.

关 键 词：第一性原理 MG2SI Mg2Ge 结构性质 弹性性质 热力学性质 

分 类 号：TG146.22[一般工业技术—材料科学与工程]