Nb_2AsC结构及热力学性质的第一性原理研究

Ab Initio Calculation of Structural and Thermodynamic Properties of Nb_2AsC

采用基于密度泛函理论的第一性原理方法研究Nb2AsC的结构、弹性和热力学性质,与其他实验值和理论值相比,该文计算的Nb2AsC晶体结构常数、体弹模量及其对压力的一阶偏导均与之符合较好;计算获得的常压弹性常数与其他理论值比较一致,由此根据力学稳定性准则,判定六方晶系Nb2AsC是力学稳定结构。预测了Nb2AsC的杨氏模量。结果表明,六方晶系Nb2AsC是各向异性。采用准谐德拜模型,模拟了压力和温度对Nb2AsC的等容热容、等温弹性模量、热膨胀系数和德拜温度等热力学性质的影响。

The structural and thermodynamic properties of Nb2AsC have been investigated with the first-principles density functional theory computations.The calculated equilibrium structural parameters agree well with the available experimental and theoretical values of Medkour et al.The calculated elastic constants are in excellent agreement with the theoretical values at ambient pressure.The elastic constant indicates that hexagonal structure Nb2AsC is mechanically stable at ambient pressure.Also,the elastic anisotropy is examined through the computation of the Young’s modulus.Based on quasi-harmonic Debye model,the thermodynamic properties including the adiabatic bulk modulus,thermal expansion coefficient,Debye temperature and heat capacity at constant volume under high temperature and pressure are predicted.