高压下3C-SiC的电子结构、弹性与热力学性质

The electronic structure,elastic and thermodynamic properties of 3C-SiC at high pressure

运用密度泛函理论的超软赝势平面波方法对3C-SiC晶体结构进行了几何优化,得到与实验值相符的晶格参数,在压强为0～100 GPa范围内对3C-SiC的电子结构与弹性进行了计算,结果表明晶体结构是稳定的,且带隙随着压强的增大而减小。然后利用准谐德拜模型研究了3C-SiC在温度为0～2 100 K、压强为0～100 GPa范围内的热力学性质,结果表明其等容热容、热膨胀系数及熵函数都随温度的升高而增大,随压强的增大而减小,而德拜温度随温度的升高而减小,随压强的增大而增大。

The crystal structure of 3C-SiC was optimized by the first-principle plane-wave density functional theory super-soft pseudo-potential method. We obtained the lattice parameter which consistent with experimental value. The electronic structure and elastic constants were calculated at 0 up to 100 GPa pressure. The result shows the structure of 3CSiC is stable, and the energy gap decreases as the pressure increases. The thermodynamic properties of 3C-SiC was obtained in the temperature from 0 to 2 100 K and pressure from 0 to 100 GPa through the quasi-harmonic Debye model. When the temperature increases or the pressure decreases, the heat capacity, thermal expansion coefficient and entropy increase, while Debye temperature decreases.