Carbon-Free Fullerenes: Condensed and Stuffed Anionic Examples in Indium Systems

Condensed, well-ordered analogs of the fullerenes occur in the hexagonal phases Na 96 In 97 Z 2 (Z = nickel, palladium, or platinum). Large cages of In 74 ( D 3 h ) and M 60 (= In 48 Na 12 , D 3 d ) share pentagonal faces to generate a double—hexagonal close-packed analog of NiAs. All these polyhedra are centered by partially disordered In 10 Z clusters within deltahedra of sodium atoms that cap all inner faces of the cages, namely, Z@In 10 @Na 39 @In 74 and Z@In 10 @Na 32 @Na 12 In 48 "onions." The highest filled bands in these compounds apparently involve localized electron pairs on surface features on In 74 -based layers. Structural and electronic relations between diamond and Naln (stuffed diamond structure) parallel those between certain fullerenes and Na 96 In 97 Z 2 and, presumably, other valence-driven intermetallic phases.