Inelastic neutron scattering from solid krypton at 10 °K

The phonon dispersion of fcc krypton has been measured along high-symmetry directions at 10 ^∘{}K on a single crystal with an equilibrium lattice spacing of 5.646 ±{} 0.002 A. The data can be fitted with a general three-neighbor-force-constant model of nine parameters with only slight depatures from central force axially symmetric conditions. Utilizing theoretical estimates of the weak additional forces due to the fourth- through eighth-nearest neighbors, the zero-sound elastic constants are determined to be c₁₁=514±5, c₁₂=284±6, and c₄₄=268±3×10⁸ dyn cm^-2. The agreement of the measured dispersion curves with theoretical calculations by Barker etal. is excellent; the maximum deviation of {}3% occurs near the zone boundary. A broadening of the neutron response for zone-boundary modes was observed that was comparable to the energy itself when the sample was near its melting point.