  Based on the interplay of theory and experiment, a large new family of filled
group 9 (Co, Rh and Ir) skutterudites is designed and synthesized. The new
materials fill the empty cages in the structures of the known binary CoSb3,
RhSb3 and IrSb3 skutterudites with alkaline, alkaline earth, and rare earth
atoms to create compounds of the type AyB4X12; A atoms fill the cages to a
fraction y, B are the group 9 transition metals, and X is a mixture of
electronegative main group elements chosen to achieve chemical stability by
adjusting the electron counts to electron-precise values. Forty-three new
compounds are reported, antimony-tin and phosphorous-silicon based, with 63
compositional variations presented. The new family of compounds is large and
general. The results described here can be extended to the synthesis of
hundreds of new group 9 filled skutterudites.
