Synthesis, crystal and electronic structures, and electrical properties ofRb2Mo12Se14 containing trioctahedral Mo-12 clusters

The synthesis of the new ternary molybdenum chalcogenide Rb2Mo12Se14 is rep orted. It crystallizes in the trigonal space group <R(3)over bar> with hexa gonal 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 M o12Se14 cluster unit, which is also found in Cs2Mo12Se14. Electrical resist ivity measurements performed on a single crystal indicate that Rb2Mo12Se14 is a metallic conductor with an unusual temperature dependence of its resis tivity. Moreover, a superconducting transition was observed at 2.5 K. Exten ded Huckel tight-binding (EHTB) calculations have been made and are discuss ed. (C) 1999 Elsevier Science Ltd.