Abstract
Introducing guests into a host framework to form a so called inclusion compound can be
used to design materials with new and fascinating functionalities. The vast majority of
inclusion compounds have electropositive guests with neutral or negatively charged
frameworks. Here, we show a series of electronegative guest filled skutterudites with inverse
polarity. The strong covalent guest-host interactions observed for the electronegative group
VIA guests, i.e., S and Se, feature a unique localized “cluster vibration” which significantly
influences the lattice dynamics, together with the point-defect scattering caused by element
substitutions, resulting in very low lattice thermal conductivity values. The findings of
electronegative guests provide a new perspective for guest-filling in skutterudites, and the
covalent filler/lattice interactions lead to an unusual lattice dynamics phenomenon which can
be used for designing high-efficiency thermoelectric materials and novel functional inclusion
compounds with open structures.
