CuAlO_2的相变和热力学性质的理论计算

The oretical calculations of phase transition and thermodynamic of CuAlO_2

采用基于密度泛函理论(DFT)的平面波赝势方法,用广义梯度近似(GGA)作为交换关联势,分别计算了CuAlO2的三角形(3R)和六角形(2 H)两种结构之间的相变及其热力学性质.通过分析能量-体积的关系,发现从3R到2 H的相变压强是27.5GPa.通过准谐德拜模型,得到了三角形(3R)和六角形(2 H)两种结构CuAlO2的热力学性质,其中包括德拜温度ΘD,热熔CV,热膨胀系数α和格林艾森参数γ在温度0-800K和压强0-27.5GPa及27.5-100GPa时的变化情况.通过对CuAlO2的能带结构进行分析,得知零压下价带在L点取得最大值,而在导带的Г点取得最小值,帯隙为1.858eV.

The electronic and thermodynamic properties and the phase transition from trigonal 3R to hex-agonal 2 H structure with high pressure for CuAlO2 are investigated from first-principles calculations u-sing norm-conserving pseudopotential with a generalized gradient approximation（GGA）for exchange and correlation.Through the analysis of energy-volume variation,we find that the phase transition of CuA-lO2 from 3R to 2H structure occurs at 27.5 GPa.By using the quasi-harmonic Debye model,the ther-modynamic properties including the Debye temperature,heat capacity,thermal expansion coefficient and Grüneisen parameter are successfully obtained in the temperature range from 0 to 800 K and the pressure form 0 to 27.5 GPa and 28 to 100 GPa for CuAlO2 3R and 2H phases,respectively.Analysis of band structures suggests that the CuAlO2 has an indirect band gap where the valence band maximum is at the L point and the conduction minimum locates atΓpoint.The calculated energy gap is 1.858 eV.