$α$-1，3，5-三硝基-1，3，5-三嗪烷（$α$ - RDX）的压力、温度和取向相关的热导率
Pressure, temperature, and orientation dependent thermal conductivity of $α$-1,3,5-trinitro-1,3,5-triazinane ($α$-RDX)
摘要：
我们使用反向非平衡分子动力学（RNEMD）模拟来确定在$α$ -RDX的热导率在<100><010>，和<001>结晶方向。用Smith-Bharadwaj非反应性经验原子间势[Smith & Bharadwaj，J.Phys.Chem.B103，3570（1999）]进行模拟，其以良好的精度表示RDX的热弹性性质。作为一个例子，我们报告的晶格常数的温度和压力的依赖性的$α$ -RDX，比较以及与实验和从头计算的结果，线性和体积热膨胀系数，我们也计算。我们发现，在200- 400 K范围内，由于声子平均自由程的减小，热导率与温度的倒数呈线性关系，热导率也表现出各向异性，在300 K时，热导率与温度的最大差值为24%<001><010>，这种效应随温度的升高而保持。该方向的热导率<100>主要在两个其他方向之间，尽管预测<001>在高温下和<010>在压力下的低温下会发生交叉。我们观察到，热导率随压力线性变化，高达4 GPa。数据拟合的分析功能内插/外推和连续模拟中使用。在293 K和常压下，对RDX单晶进行了脉冲受激热散射（ISTS）实验，验证了MD结果的正确性，结果表明MD结果与实验结果具有良好的定性和定量一致性：三个主取向之间的有序度相同，实验与模型的平均误差为10%。这些结果提供的信心，提取的分析功能，使用RNEMD方法和Smith-Bharadwaj潜力可以应用到模型的导热系数的$α$ -RDX。
英文摘要：
We use reverse non-equilibrium molecular dynamics (RNEMD) simulations to determine the thermal conductivity in $α$-RDX in the <100>, <010>, and <001> crystallographic directions. Simulations are carried out with the Smith-Bharadwaj non-reactive empirical interatomic potential [Smith & Bharadwaj, J. Phys. Chem. B 103, 3570(1999)], which represents the thermo-elastic properties of RDX with good accuracy. As an illustration, we report the temperature and pressure dependence of lattice constants of $α$-RDX, which compare well with experimental and ab initio results, as do linear and volume thermal expansion coefficients, which we also calculate. We find that the thermal conductivity depends linearly on the inverse temperature in the 200-400K regime due to the decrease in the phonon mean free path. The thermal conductivity also exhibits anisotropy, with a maximum difference at 300K of 24% between the <001> and <010> directions, an effect that remains when temperature increases. Thermal conductivity in the <100> direction is mostly between the two other directions, although crossovers are predicted with <001> at high temperature, and <010> at low temperature under pressure. We observe that the thermal conductivity varies linearly with pressure up to 4 GPa. The data are fitted to analytical functions for interpolation/extrapolation and use in continuum simulations. MD results are validated against experiments using impulsive stimulated thermal scattering (ISTS) on RDX single crystals at 293K and ambient pressure, showing good qualitative and quantitative agreement: same ordering between the three principal orientations, and an average error of 10% between the experiments and the model. These results provide confidence that the extracted analytical functions using the RNEMD methodology and the Smith-Bharadwaj potential can be applied to model the thermal conductivity of $α$-RDX.
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