Diffuse scattering study by X-ray and neutron diffraction measurement and phonon dispersion relation

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The oscillatory forms of the diffuse scattering intensities were observed from ordered crystals at room temperature. The observed diffuse scattering intensities were analyzed by including the correlation effects among thermal displacements of atoms. The values of correlation effects decrease rapidly with the increase of inter-atomic distances. From the parameters of Debye-Waller temperature factor and the values of correlation effects, the inter-atomic force constants among first, second and third nearest neighboring atoms were determined. A rough estimation of phonon dispersion relation was performed from the inter-atomic force constants and crystal structure using computer simulation.