Computer simulation and neutron scattering studies of lattice dynamics of Ba1−xKxBiO3

On the basis of a simple model for the interatomic potential the lattice dynamics of Ba 1−x K x BiO 3 were calculated. Some features of the structural phase diagram, the optical and neutron spectroscopy data can be explained in spite of the simplicity of the model. To compare the model calculations with the experiment a time-of-flight neutron scattering study of the lattice dynamics of Ba 1−x K x BiO 3 for x =0.0 and x =0.4 has been performed for the temperatures 10 K, 80 K and 290 K. The experimental results are in good agreement with previous measurements. No temperature effects were found for the generalized phonon density of states. The phonon spectrum of a superconducting sample reveals fewer Van Hove singularities and softens in comparison with that of the nonsuperconducting one. The calculated phonon density of states was found to be in qualitative agreement with experiment.