CuAlSe2在高压下结构、弹性、热学性质的第一性原理计算
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O521+.2

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Elastic and electronic properties of CuAlSe2 under pressure: A first-principle study
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    摘要:

    本文中我们运用第一性原理平面赝势密度泛函理论,研究了四方晶体CuAlSe2的结构、弹性性质以及热力学性质。首先通过状态方程拟合找到零温零压时的平衡体积、晶格常数、体弹模量B0以及其对压强的一阶导数 。接着分析了相对晶格常数a/a0 、c/c0以及相对体积V/ V0随压强的变化趋势。我们也研究了弹性常数随压强增大的变化趋势,C11、C33、C12、C13随着压强的增大而增大,C44和C66确随着压强的增加保持一个平稳的值基本不变。计算也表明在15GPa以前CuAlSe2的弹性常数都满足力学稳定性,表明在15GPa以前都不发生相变,与实验结果相吻合。在零温零压下我们计算得到的弹性常数和体弹模量和其它理论值实验值都比较符合。然后根据准谐德拜模型,我们分析了热膨胀系数以及比热容随压强和温度的变化关系。最后我们分析了CuAlSe2晶体在零温零压和高压下的态密度图,简单了解了一下电子结构的变化情况。

    Abstract:

    We employ the first-principles plane wave method in the frame of density functional theory (DFT) to investigate the equilibrium lattice structure, the mechanic, thermodynamic and electronic properties of CuAlSe2 compound. The lattice constants, the bulk modulus B0 and its pressure derivative B0’ are calculated. Based on the quasi-harmonic Debye model, we also obtain thermal expansion coefficient. It is noteworthy that the variation tendencies of these parameters are investigated detailed with pressure. In addition, we also calculate the elastic constants of CuAlSe2 compound. Results show that the elastic constants C11、C33、C12 and C13 increase with increasing pressure, whereas the influences of pressure on elastic constant C44 and C66 are not obvious. The calculated elastic constants satisfy the hecriterion of mechanical until the pressure grows to more than 15GPa, which suggests the structure phase transition of CuAlSe2 may be happened. We also investigate the shear sound velocity VS, longitudinal sound velocity VL, and Debye temperature ΘE from our elastic constants, as well as the thermodynamic properties from quasi-harmonic Debye model. We obtain the dependence between the heat capacity Cv and pressure, and the same as thermal expansion coefficient α. At last, the pressure dependences of band structures and density of states are also investigated, which shows that the value of TDOS decreases with the increase of the pressure.

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引用本文格式: 周梦,卢志鹏,陶应奇,黄鳌,周乐,周晓云,胡翠娥. CuAlSe2在高压下结构、弹性、热学性质的第一性原理计算[J]. 四川大学学报: 自然科学版, 2017, 54: 771.

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  • 收稿日期:2017-05-17
  • 最后修改日期:2017-06-06
  • 录用日期:2017-06-07
  • 在线发布日期: 2017-06-27
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