CRYSTAL AND ELECTRONIC BAND-STRUCTURE OF IRTE2 - EVIDENCE OF ANIONIC BONDS IN A CDI2-LIKE ARRANGEMENT

The Rietveld structure determination of IrTe2 showed that this phase differs from the CdI2-like arrangement, with Te-Te multiple bonds (mean d(Te-Te) = 3.528 angstrom) corresponding to Te-1.5 anions, in agreement with the charge balance Ir3+(Te-1.5)2, the Iridium ion being d6 low spin. This new polymeric-CdI2 structural type is shared by several other tellurides, namely: RhTe2, CoTe1.7, NiTe1-x, PdTe2, and PtTe2, and its occurrence explains the abnormally low c/a ratio (1.38) of the hexagonal cell parameters. IrTe2 band structure shows a strong degree of hybridization and mixing between the d cationic and p anionic levels. From the negative total overlap population between neighbour Ir3+ cations at the Fermi level, it can be inferred that the metallic conductivity of the phase involves the Tellurium anions through their 3D network. The crystal orbital overlap population curves for the Te-Te bonds indicate that electrons donated to the compound should fill anti-bonding levels, allowing for a breaking of these links, and possibly restoring a classical anionic stacking.