METAL-RICH MIXED CHALCOGENIDES TANI(2)Q(2) (Q = SE, TE) - SYNTHESIS, STRUCTURE AND ELECTRONIC-PROPERTIES

Phases in the pseudo-binary system TaNi2SexTe2-x (0 less than or equal to x less than or equal to 1) have been prepared by high temperature methods. According to the results of powder X-ray diffraction all phas es crystallize isotypic to TaNi2Te2 in the orthorhombic space group Pn ma (no. 62). The lattice parameters in the TaNi2SexTe2-x system show a complex behaviour as a function of composition. The structure of TaNi 2SeTe was determined by single crystal methods. TaNi2SeTe is built up from TaNi2-layers which are sandwiched by chalcogen sheets. The chalco gen atoms are ordered on two independent crystallographic postitions. In agreement with size considerations the Se atoms have four metal nei ghbours while the Te atoms have five neighboring metal atoms. We have not been able to achieve a substitution by Se on the Te site with five metal neighbours so far. TaNi2SeTe is metallic and shows Pauli parama gnetic behaviour, as expected from the results of TB-LMTO-ASA band str ucture calculations.