Single crystals of Rb₄C₆₀: Synthesis and structure determination

Single crystals of Rb₄C₆₀ were obtained at 973 K in a closed niobium ampule, and the structure was determined by X-ray diffraction (|4|mmm, Z=2,a = b = 11.9783(17) Å, c = 11.035(2) Å, and V= 1583.3(4) ų. The refinement was successful without any bond distance restraint and resulted in average C-C bond lengths of d(6:6) = 1.383(5) Å and d(5:6) = 1.453(5) Å. C₆₀^4- is rotationalfy disordered and has the shape of a distorted truncated icosahedron (D_2h). Using the new structural data, density functional theory calculations obtain a metallic ground state.