Neutron Scattering Study of Lattice Dynamics in CuBr. II. Anharmonic Effect on Debye-Waller Factor

Abstract

Integrated intensities for the Bragg reflections of neutrons from CuBr single crystal with zincblende structure were measured at several temperatures. The experimental data both at room temperature and higher temperatures were interpreted consistently in terms of Matsubara’s representations for anharmonic Debye-Waller factor. The harmonic and cubic anharmonic potential parameters for each atom obtained by the least squares refinement are α_Cu=0.937, α_Br=1.49 (×10⁻¹² erg Å⁻²) and β_Cu=1.00 (×10⁻¹² erg Å⁻³). A discrepancy was found between the harmonic component of the mean square displacement of the Cu atom and that calculated from the phonon dispersion relation reported in Part I. In view of the lattice dynamical study by inelastic neutron scattering, the effects of the quartic anharmonicity which were ignored are considered to be included in the harmonic component determined in this analysis.