Metal-rich mixed chalcogenides TaNi2Q2 (Q=Se,Te): synthesis, structure and electronic properties

Abstract

Phases in the pseudo-binary system TaNi2SexTe2x (0x1) have been prepared by high temperature methods. According to the results of powder X-ray diffraction all phases crystallize isotypic to TaNi2Te2 in the orthorhombic space group Pnma (no. 62). The lattice parameters in the TaNi2SexTe2x system show a complex behaviour as a function of composition. The structure of TaNi2SeTe was determined by single crystal methods. TaNi2SeTe is built up from TaNi2-layers which are sandwiched by chalcogen sheets. The chalcogen atoms are ordered on two independent crystallographic postitions. In agreement with size considerations the Se atoms have four metal neighbours 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 paramagnetic behaviour, as expected from the results of TB-LMTO-ASA band structure calculations.