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

Abstract

Condensed, well-ordered analogs of the fullerenes occur in the hexagonal phases Na₉₆In₉₇Z₂ (Z = nickel, palladium, or platinum). Large cages of In₇₄ (D_3h) and M₆₀ (= In₄₈Na₁₂, D_3d) share pentagonal faces to generate a double—hexagonal close-packed analog of NiAs. All these polyhedra are centered by partially disordered In₁₀Z clusters within deltahedra of sodium atoms that cap all inner faces of the cages, namely, Z@In₁₀@Na₃₉@In₇₄ and Z@In₁₀@Na₃₂@Na₁₂In₄₈ "onions" The highest filled bands in these compounds apparently involve localized electron pairs on surface features on In₇₄-based layers. Structural and electronic relations between diamond and Naln (stuffed diamond structure) parallel those between certain fullerenes and Na₉₆In₉₇Z₂ and, presumably, other valence-driven intermetallic phases.