论文标题
热力学特性的密度功能研究，高温区域的热力学特性，热膨胀和晶格导热率
Density functional study of thermodynamic properties, thermal expansion and lattice thermal conductivity of Fe$_{2}$VAl at high temperature region
论文作者
论文摘要
在这里，我们介绍了热力学性能，热力扩展和晶格的导热率的声子计算，在$ 300-800 $ K的温度范围内，与现有实验相比，温度范围为$ _ {2} $ val。使用有限位移方法和超级细胞方法计算声子分散。所有声子模式的正频率表明化合物的机械稳定性。在谐波近似下计算恒定体积和Helmholtz自由能的特定热量，而在准谐波近似下进行热膨胀的计算。晶状体导热率（$κ_{l} $）是使用第一原则的Anharmonic晶格动力学计算计算的。零点能量和Debye温度分别计算为$ \ sim $ 21 kj/mol和638 K。发现计算出的热扩展为$ \ sim $ 6.3 $ \ times $ 10 $^{ - 6} $ k $^{ - 1} $和$ \ sim $ 7.2 $ \ times $ 10 $^{ - 6} $ k $^{ - 1} $ at 300和800 k，分别为300和800 k。在300 k处观察到计算得的（$ \ sim $ 48.6 w/m-k）与$κ_{l} $的实验（$ \ sim $ 22.8 w/m-k）值之间的偏差。但是，随着温度的升高，随着温度的升高，计算出的$κ__{l} $与$ $ \ sim $ 11 $ \ sim $ 18.2 w/sim n.2 w.2 w/m-k时为800。解决了$κ_{l} $偏差的可能原因。计算声子寿命的温度依赖性，以了解$κ_{l} $的功能。目前的研究表明，基于DFT的语音计算为Fe $ _ {2} $ val的可用实验声子相关属性提供了相当好的解释，高温范围为$ 300-800 $K。
Here, we present the phonon calculations for thermodynamic properties, thermal expansion and lattice thermal conductivity of Fe$_{2}$VAl in the temperature range of $300-800$ K and compared with existing experiment. Phonon dispersion is computed using finite displacement method and supercell approach. The positive frequencies of all the phonon modes indicate the mechanical stability of the compound. The specific heat at constant volume and Helmholtz free energy are calculated under harmonic approximation, while calculation of thermal expansion is done under quasi-harmonic approximation. Lattice thermal conductivity ($κ_{L}$) is calculated using first-principle anharmonic lattice dynamics calculations. The zero-point energy and Debye temperature are computed as $\sim$21 kJ/mol and 638 K, respectively. The calculated thermal expansions are found to be $\sim$6.3 $\times$ 10$^{-6}$ K$^{-1}$ and $\sim$7.2 $\times$ 10$^{-6}$ K$^{-1}$ at 300 and 800 K, respectively. A significant deviation between calculated ($\sim$48.6 W/m-K) and experimental ($\sim$22.8 W/m-K) values of $κ_{L}$ are observed at 300 K. But, as the temperature increases, the calculated and experimental $κ_{L}$ come closer with the corresponding values of $\sim$18.2 W/m-K and $\sim$11.0 W/m-K at 800. The possible reasons for the deviation of $κ_{L}$ are addressed. The temperature dependent of phonon lifetime is computed in order to understand the feature of $κ_{L}$. Present study suggests that DFT based phononic calculations provide reasonably good explanations of available experimental phonon related properties of Fe$_{2}$VAl in the high temperature range of $300-800$ K.
