根据第一性原理计算的ZrC和HfC的温度相关力学性能
Temperature-dependent mechanical properties of ZrC and HfC from first principles
摘要：
为了深入了解高温对ZrC和HfC力学性能的影响，采用两种不同的方法（第一性原理准谐近似和第一性原理准静态近似）系统地研究了这两种碳化物的弹性常数随温度的变化.随着温度的升高，ZrC和HfC的等熵C $_{11}$逐渐减小，等熵C $_{12}$略有增加。而ZrC和HfC的等熵C $_{44}$对温度不敏感。在ZrC和HfC的情况下，从QHA计算的温度依赖性C $_{11}$的下降比从QSA更明显。温度对弹性模量，泊松比，弹性各向异性，硬度和断裂韧性的影响进行了进一步探讨和讨论。结果表明，在高温下，由QHA估算的B、G和E的降解比由QSA估算的降解严重。从室温到2500 K，理论上的下降斜率（来自QHA）为0.38 GPa $\cdot$ K $^{-1}$，0.30 GPa $\cdot$ K $^{-1}$，和0.32 GPa的$\cdot$ K $^{-1}$的ZrC和0.33 GPa的$\cdot$ K $^{-1}$，0.29 GPa $\cdot$ K $^{-1}$，对于HfC，为0.30 GPa的$\cdot$ K $^{-1}$。
英文摘要：
In order to gain insight into the effect of elevated temperature on mechanical performance of ZrC and HfC, the temperature-dependent elastic constants of these two carbides have been systematically studied using two different methods (first-principles qusi-harmonic approximation and first-principles qusi-static approximation). Isoentropic C$_{11}$ gradually decrease and the isoentropic C$_{12}$ slightly increases for ZrC and HfC under temperature. While the isoentropic C$_{44}$ of both ZrC and HfC is insensitive to the temperature. In both ZrC and HfC cases, the decline of temperature-dependent C$_{11}$ calculated from QHA is more pronounced than from QSA. Temperature effects on modulus of elasticity, poisson's ratio, elastic anisotropy, hardness and fracture toughness are further explored and discussed. The results indicate that degradation of B, G and E estimated from QHA is more serious than these from QSA at high temperature. From room temperature to 2500 K, the theoretical decreasing slope (from QHA) of B, G, and E is 0.38 GPa$\cdot$K$^{-1}$, 0.30 GPa$\cdot$K$^{-1}$, and 0.32 GPa$\cdot$K$^{-1}$ for ZrC and 0.33 GPa$\cdot$K$^{-1}$, 0.29 GPa$\cdot$K$^{-1}$, and 0.30 GPa$\cdot$K$^{-1}$ for HfC.
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