SYNTHESIS, CRYSTAL AND ELECTRONIC STRUCTURES, AND ELECTRICAL PROPERTIES OF Rb_2Mo_12Se_l4 CONTAINING TRIOCTAHEDRAL Mo_l2 CLUSTERS

摘要

The synthesis of the new ternary molybdenum chalcogenide Rb_2Mo_12Se_14 is reported. lt crystallizes in the trigonal space group R_3 with hexagonal lattice parameters a = 9.538 (2) and c = 24.66 (l) A. The main structural building block of the crystal structure of Rb_2Mo_12Se_14 is the Mo_12Se_14 cluster unit, which is also found in Cs_2Mo_12Se_14 Electrical resistivity measurements performed on a single crystal indicate that Rb_2Mo,12~Se_14 is a metallic con- ductor with an unusual temperature dependence of its resistivity. Moreover, a superconducting transition was observed at 2.5 K. Extended Hhckel tight- binding (EHTB) calculations have been made and are discussed.