高压下Ni3Al热力学性质的第一性原理研究

运用第一性原理方法结合准谐Debye-Grüneisen模型研究了高压下Ni3Al的热力学性质，拟合了Ni3Al的状态方程，计算了不同压强下Ni3Al的弹性模量及吉布斯自由能等热力学性质随温度的变化关系. 计算结果表明：采用七阶Birch-Murnaghan方程拟合的晶格常数与实验测量结果吻合较好；零压下弹性模量、吉布斯自由能、焓、熵、热容和体膨胀系数随温度的变化与实验值符合较好；在特定压强下，Ni3Al的弹性模量和吉布斯自由能随温度升高而减小，焓、熵随温度升高而增加；预测的德拜温度约为500K，与实验值符合较好.

Thermodynamic properties of Ni3Al under pressure via first-principles calculations

Within the framework of the quasiharmonic Debye-Grüneisen approximation, the equation of state and thermodynamics properties of Ni3Al under pressure have been studied using the first-principles projector-augmented wave method. The results reveal that the lattice constants from the seven-order Birch-Murnaghan equation are in agreement with the experimental data. The calculated Gibbs free energy, enthalpy, entropy, heat capacity and volume thermal expansion coefficient of Ni3Al at 0 GPa as a function of temperature are consistent well with the experimental data. At different pressures, the bulk modulus and Gibbs free energy decrease but the enthalpy and entropy increase with the increasing of temperature. The estimated Debye temperature of Ni3Al from heat capacity at constant volume is 500 K. The value is in agreement with the available measured values.