Zr_4Al_2高压下热动力学性质的第一性原理研究

Thermodynamic properties of Zr_4Al_2 under high pressure from first-principles calculations

本文主要通过平面波赝势密度泛函理论的第一性原理计算方法,采用广义梯度近似(GGA)交换相关函数,研究了六角结构的Zr_4Al_2的EOS态方程和热动力学性质.通过采用了声子效应的准谐近似德拜模型,我们成功得到了晶胞体积V随温度以及V/V_0、德拜温度(?)、热熔C_V随压强P的变化关系.另外,我们还研究了热膨胀系数α及格林参数γ随温度和压强的变化关系,计算结果表明格林参数和热膨胀系数随温度的升高而增加,但是在较高的温度下,热膨胀系数几乎不受温度的影响.

The equations of state （EOS） and other thermodynamic properties of the hexagonal structure Zr4A12 are investigated by using a firstprinciples plane wave method planewave pseudopotential density functional theory method in the frame of the generalized gradient approximation （GGA）. The obtained results are consistent with the experimental data and those calculated by others. Through the quasihar monic Debye model, in which the phononic effects are considered, the dependences of relative volume V/ V0 on pressure P, cell volume V on temperature T, and Debye temperature and specic heat Cv on pres sure P are successfully obtained. The variation of the thermal expansion a as well as Graneisen paramter with temperature and pressure is investigated, which shows the thermal expansion a as well as Grtineisen paramter 7 increase with increasing temperature but the temperature has hardly any effect on the thermal expansion a at higher pressure.