论文标题
使用Quasi-Continuum近似的基于扰动理论的晶格导热率模型的定量评估
Quantitative assessment of perturbation theory-based lattice thermal conductivity models using quasi-continuum approximation
论文作者
论文摘要
分散关系，各向异性和布里鲁因区结构对晶格动力学的谐波近似扰动理论方法的影响。各向异性非线性弹性连续体已被视为声子分散和布里鲁因区域的各种水平，并用Grüneisen参数用作平均晶体非谐波度量度。此外，比较了不同模型的热导率预测用于处理声子碰撞算子的非对角元素的治疗。对于模型系统，具有相对较高的各向异性比率的氩气表明，对各向异性的解释对于准确确定可用的相位空间至关重要。此外，即使对于立方系统，也发现了广泛扩展的近似值，例如各向同性连续体和单模式放松时间。这些近似值的成功证明是误差取消的直接结果。通过基准反对我们的Boltzmann传输方程的迭代解决方案，该方程与实验性氩气（2-80 K）的实验热导率数据达到了极好的一致性，我们表明了考虑在声子模式下使用声子散射术语的耦合术语的重要性，而不是在统计平均含义中，例如，Callaway模型在统计平均含义中也是如此。此外，我们的结果表明了与分子动力学发现一致的相干声子散射在熔点温度附近起作用的作用，这是通过粒子样音子（不一致的散射）和由于声子相干散射引起的粒子样音子（不一致的散射）介导的热扩散之间的交叉的证据。此外，电导率预测对声子频谱的敏感性在温度上发生了变化。
The impact of dispersion relations, anisotropy, and Brillouin zone structure on intrinsic phonon scattering rates has been assessed within the harmonic approximation-perturbation theory approach for lattice dynamics. Anisotropic nonlinear elastic continuum has been considered with various levels of representation of phonon dispersion and Brillouin zone shape, and with Grüneisen parameter used as an average measure of crystal anharmonicity. In addition, thermal conductivity prediction of different models for the treatment of the off-diagonal elements of phonon collision operator are compared. For a model system, argon, with a relatively high anisotropy ratio, the results show that accounting for anisotropy is critical for accurate determination of available phase space for 3-phonon scattering and scattering rates. Moreover, widely spread approximations such as isotropic continuum and Single Mode Relaxation Time are found unreliable, even for cubic systems. The success of these approximations is demonstrated to be a direct result of error cancellations. By benchmarking against our iterative solution of Boltzmann Transport Equation, which achieves excellent agreement with experimental thermal conductivity data for solid argon (2-80 K), we show the essential importance of considering coupling terms of phonon scattering kernel at phonon mode level, and not in a statistical average sense as, for example, Callaway model does. Moreover, our results manifest the role played by coherent phonon scattering near the melting temperature, in agreement with molecular dynamics findings, which serves as an evidence for the crossover between heat diffusion mediated by particle-like phonons (incoherent scattering) and wave-like heat propagation due to phonon coherent scattering. Furthermore, sensitivity of conductivity prediction to phonon spectrum is revealed to change over temperature.
