Synthesis, crystal and electronic structures, and electrical properties of Rb2Mo12Se14 containing trioctahedral Mo12 clusters

The synthesis of the new ternary molybdenum chalcogenide Rb2Mo12Se14 is reported. It crystallizes in the trigonal space group <R(3)over bar> with hexagonal lattice parameters a = 9.538 (2) and c = 24.66 (1) Angstrom. The main structural building block of the crystal structure of Rb2Mo12Se14 is the Mo12Se14 cluster unit, which is also found in Cs2Mo12Se14. Electrical resistivity measurements performed on a single crystal indicate that Rb2Mo12Se14 is a metallic conductor with an unusual temperature dependence of its resistivity. Moreover, a superconducting transition was observed at 2.5 K. Extended Huckel tight-binding (EHTB) calculations have been made and are discussed. (C) 1999 Elsevier Science Ltd.