Correlation effects among thermal displacements of atoms in KBr

Neutron diffraction measurements have been performed on powder KBr at 7 and 298 K. An oscillatory diffuse scattering intensity is observed at 298 K. The oscillatory scheme of the diffuse scattering intensity is explained by the values of correlation effects which are almost the same as those in other ionic crystals. The value of the correlation effects as suggested by earlier studies using EXAFS measurement cannot explain the observed diffuse scattering intensity. Force constants among first, second and third nearest neighboring atoms are obtained from the correlation effects and used to estimate the phonon dispersion curves by computer simulation.