CoSb3 has a low 𝑍𝑇 of just 0.05 at 723 K due its high 𝜅 latt , which can reach 10 W m -1 K -1 at room temperature in single crystals. However, CoSb3 is chemically very flexible and is amenable both to doping the host framework, e.g. with transition metals and chalcogenides, and to filling the cavities with atoms including alkali and alkaline earth metals, Group III elements, chalcogens, halogens, transition metals and rare-earth elements. . This extraordinary flexibility has led to the experimental synthesis of a wide variety of compounds including examples doped at the Co and Sb sites, incorporating up to seven filler atoms, and with concomitant doping and filling. Some compositions with notable improvements to the 𝑍𝑇 include Ni0.3Co3.7Sb12 (𝑍𝑇 = 0.52 at 773 K), Na0.48Co3Sb12 (𝑍𝑇 = 1.25 at 800 K), Sr0.16Yb0.03Co4Sb11.82 (𝑍𝑇 = 1.32 at 850 K), Ba0.08La0.05Yb0.04Co4Sb12 (𝑍𝑇 = 1.7 at 850 K), Yb0.2Ba0.1Al0.1Ga0.1In0.1La0.05Eu0.05Co4Sb12 (𝑍𝑇 = 1.2 at 800 K), and Ce0.12Fe0.71Co3.29Sb12 (𝑍𝑇 = 0.8 at 750 K). First-principles modelling of the structural dynamics and thermal transport, typically using densityfunctional theory (DFT), has been instrumental in understanding the intrinsically low 𝜅 latt of flagship thermoelectrics and other highly-anharmonic materials, and has also been applied to identify novel candidate TEs. Despite a large body of experimental work on the skutterudites, there are comparatively few modelling studies on the phonon thermal transport. Guo et al. used first-principles lattice-dynamics calculations to study the thermal transport in CoSb3 and to investigate the impact of nanostructuring and Sb →