Revisiting the filling fraction limit in skutterudite structures

This work examines the filling fraction limit (FFL) in skutterudite structures using single-crystal X-ray diffraction and electronic structure calculations and concludes that there are no clear, simple trends for the FFL in skutterudites. Our analyses reveal that La is the most preferred filler among the studied fillers due to the larger increases in integrated crystal orbital Hamilton population (-ICOHP). This study also suggests that the FFL is influenced by the bonding and antibonding interactions in the structure, whose strength depends on the available valence electrons, and also by formation of the competing phases.