We present a systematic first-principles modelling study of the structural dynamics and thermal transport in CoSb₃ skutterudites with a series of noble-gas filler atoms. Filling with chemically-inert atoms provides an idealised model for isolating the effects of the fillers from the impact of redox changes to the host electronic structure. A range of analysis techniques are proposed to estimate the filler rattling frequencies, to quantify the separate impacts of the fillers on the phonon group velocities and lifetimes, and to show how changes to the phonon spectra and interaction strengths lead to suppressed lifetimes. The noble-gas fillers are found to reduce the thermal conductivity of the CoSb₃ framework by up to 15% primarily by suppressing the group velocities of low-lying optic modes. The filler rattling frequencies are determined by a detailed balance of increasing atomic mass and stronger interactions with the framework, and are found to be a good predictor of the impact on the heat transport. Lowering the rattling frequency below ∼1.5THz by selecting heavy fillers that interact weakly with the framework is predicted to lead to a much larger suppression of the thermal transport, by inducing avoided crossings in the acoustic-mode dispersion and facilitating enhanced scattering and a consequent large reduction in phonon lifetimes. Approximate rattling frequencies determined from the harmonic force constants may therefore provide a useful metric for selecting filler atoms to optimise the thermal transport in skutterudites and other cage compounds such as clathrates.

我们对具有一系列惰性气体填充原子的CoSb ₃方钴矿的结构动力学和热传输进行了系统的第一性原理建模研究。用化学惰性原子填充提供了一个理想化的模型，用于将填料的影响与氧化还原变化对主体电子结构的影响隔离开来。提出了一系列分析技术来估计填料嘎嘎声频率，量化填料对声子群速度和寿命的单独影响，并显示声子光谱和相互作用强度的变化如何导致抑制寿命。发现惰性气体填料会降低 CoSb _{3的热导率}主要是通过抑制低洼光学模式的群速度，框架最多可降低 15%。填料嘎嘎声频率由增加的原子质量和与框架的更强相互作用的详细平衡决定，并且被发现是对热传输影响的良好预测指标。通过选择与框架相互作用较弱的重质填料将嘎嘎声频率降低到 1.5THz 以下，预计会导致更大的热传输抑制，通过避免声模色散中的交叉并促进增强的散射和随之而来的大声子寿命的减少。