一维非线性无序晶格中的热导率：硬型和软型非谐性的两种散射效应
Thermal conductivity in one-dimensional nonlinear disordered lattices: Two kinds of scattering effects of hard-type and soft-type anharmonicities
摘要：
非晶态固体在理论上可以用非谐无序晶格来模拟。然而，目前对非简谐无序晶格热导率的理论研究大多集中在硬型（HT）非简谐势上。在这里，我们研究的热导率$κ$的一维（1D）无序晶格的硬和软型（ST）的非谐在位势。通过直接分子动力学模拟和理论计算发现，HT模型中$κ$的非谐性依赖是非单调的，而ST模型中则是单调增加的.这为提高无序系统的热导率提供了一种新的途径。HT模型的$κ$与准谐波Green-Kubo（QHGK）方法的预测在很大范围内是一致的，而对于ST模型，随着非谐性变软，数值结果似乎与理论预测有很大偏差. ST模型的这一新的和独特的特征可能源于这样一个事实，即只存在离域效应，而不同于HT模型中的离域效应和本地化效应。
英文摘要：
The amorphous solids can be theoretically modeled by anharmonic disordered lattices. However, most of theoretical studies on thermal conductivity in anharmonic disordered lattices only focus on the potentials of hard-type (HT) anharmonicity. Here we study the thermal conductivity $κ$ of one-dimensional (1D) disordered lattices with both hard- and soft-type (ST) anharmonic on-site potentials. It is found, via both direct molecular dynamic simulations and theoretical method, that the anharmonicity dependence of $κ$ in the HT model is nonmonotonous, while in the ST model is monotonously increased. This provides a new way to enhance thermal conductivity in disordered systems. Furthermore, $κ$ of the HT model is consistent with the prediction of the quasi-harmonic Green-Kubo (QHGK) method in a wide range of anharmonicity, while for the ST model, the numerical results seem largely deviated from the theoretical predictions as the anharmonicity becomes soft. This new and peculiar feature of the ST model may root in the fact that only delocalization effect exists, different from the competing roles that both delocalization and localization play in the counterpart HT model.
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