Influence of substitutional impurities on the static and dynamical behaviour of K2OsCl6 in the vicinity of the structural phase transition: A neutron diffraction study

The effect of IrCl62− and ReCl62− impurity ions substituted for OsCl62− ion in K2OsCl6 is studied using neutron powder diffraction. The introduction of the impurity ions causes measurable changes in the lattice parameters but not in the Os—Cl bond length. The dynamical parameters of the model structure used to fit the data are well described by a Debye model of the lattice vibrations. The structural phase-transition temperature is affected by the addition of the impurity ions. Evidence is provided for suppression, in the presence of the impurities, of the development of precursor dynamical clusters above the phase-transition temperature.