Dynamic charge disproportionation in the 1D chain material PdTeI

PdTeI features quasi-1D –Pd–Te–Pd–Te– chains with palladium formally in the 3+ oxidation state. Using pair distribution function analysis of X-ray and neutron total scattering data, we find that there is a local charge-density wave arising from the disproportionation of Pd3+ towards Pd2+ in pseudo-square planar, and Pd4+ in pseudo-octahedral, coordination. The magnitude and coherence length for this distortion is small, such that the average structure determined by Bragg diffraction techniques possesses higher symmetry than the local structure at all temperatures. Temperature-dependent resistivity measurements show a transport anomaly at TCDW = 50 K, corresponding to the reduced fluctuations of the charge separated Pd2+ and Pd4+ sites. At higher temperatures, the charge separation is dynamic, with local Pd2+/Pd4+ pairs persisting up to room temperature.