温度和压强对金属化合物Co_2Zr和Co_2Ti的结构和热力学性质影响的研究

Temperatureand pressure effects on structural and thermodynamic properties of intermetallic compounds Co_2Zr and Co_2Ti

基于平面波赝势密度泛函理论(DFT)和广义梯度近似(GGA)的第一性原理计算了高温高压下金属化合物Co_2Zr和Co_2Ti的结构和热力学性质.Co_2Zr和Co_2Ti均为立方晶体,且结构类型为Cu2Mg结构.通过计算得出的晶格参数跟实验值符合较好.用准谐德拜模型计算了Co_2Zr和Co_2Ti的热力学性质.在0~100 GPa的压强和0~1500 K的温度作用下,两种物质的德拜温度Θ,热容CV,热膨胀系数α随压强和温度的变化而变化.随着压强的增大,德拜温度单调的增加;相同压强下,Co_2Ti的德拜温度始终大于Co_2Zr.热容CV和热膨胀系数α均随温度的增加而增加,增大压强时反而减小,说明减小温度和增大压强对CV以及α有相同的影响.

The structural and thermodynamic properties of intermetallic compounds Co2Zr and Co2Ti are calculated by first principle calculations with ab initio plane-wave pseudopotential density functional theory （PWPDFT） and the generalized gradient approximation （GGA） under high temperature and pressure. Co2Zr and Co2Ti are both cubic crystals with Cu2Mg type structure. The results calculated are consistent with the experimental data. the thermodynamic properties are calculated in the quasi-harmonic Debye model. In the range of 0-100GPa pressure and 0-1500K temperature, the Debye temperature Θ, the heat capacity CV and the thermal expansion α vary with pressure and temperature. The Debye temperature increases monotonically as the pressure increases. Besides, Co2Ti has a higher Debye temperature than Co2Zr under the same pressure. Both the heat capacity CV and the thermal expansion α increase with increasing temperature whereas decrease with increasing pressure, which illustrates decreasing temperature and increasing pressure have the same effects on CV and α.