TLIN5S6 - A NEW MIXED-VALENCE TERNARY CHA LCOGENIDE AND ITS CRYSTAL-CHEMISTRY

We report about synthesis and crystal structure of the new ternary mix ed valence compound TlIn5S6, which crystallizes in the monoclinic syst em, space group P2(1)/m with the lattice constants a = 8.7960(5) Angst rom, b = 3.9129(3) Angstrom, c = 17.458(2) Angstrom, beta = 94.71(1)de grees, (Z = 2). The threedimensional atomic arrangement can be explain ed in terms of the formulation Tl+([In-2](4+))(2)(In3+)(S2-)(6), imply ing the simultaneous existence of T-l+ and In3+ besides two distinct I n-2(4+)-dumb bells with covalent bonding between In-atoms in different crystallographic surroundings. This structural principle corresponds to the already known solid In,S,, characterized by the formulation In[In-2](4+) (In3+)(3)(S2-)(7). In addition the paper contains informati on about the structurally related compounds In(4)X(3) (X = Se,Te),In5S 4,In(6)X(7) (X = S, Se), M(7)Te(10) (M = Al, Ga, In) and M(3)Te(4) (M = Ga, In) which were poorly characterized up to now.