Local structural aspects of metal-metal transition in IrTe$_{\mathrm{2}}$ from x-ray PDF

Evolution of local atomic structure across the metal-metal transition in IrTe$_{\mathrm{2}}$ is explored by pair distribution function (PDF) analysis of x-ray total scattering data over 80 K \textless T \textless 300 K range. Local and average structures are found to be in accord at all temperatures conforming to P-1 and P-3m1 symmetry at low and high temperature, respectively. We find no evidence of short-range Ir-dimers surviving into the high-T regime, in stark contrast to the earlier EXAFS study proposing Ir-dimer order-disorder mechanism. Phase fraction obtained from explicit 2-phase structural modeling displays hysteretic behavior across the transition, in agreement with electronic transport measurements, indicative of a strong tie between the lattice and electronic configurations. Bond valence methodology applied to structural parameters further indicates significant bond charge disproportionation in association with the transition.