Anharmonic Thermal Scattering of X-Rays from Cubic Metals

Abstract

Thermal diffuse scatterings of X-rays by the lowest-order anharmonic vibration of cubic metals are investigated. The scattering which can be regarded as an interference between the harmonic one-phonon and two-phonon scatterings gives rise to asymmetry in the scattering around the reciprocal lattice point. The intensity formula is expressed as products of the elements of the inverse dynamical matrices in the high-temperature approximation. In terms of the inverse dynamical matrix elements for wave vectors up to 4000 in the first Brillouin zone, the intensity distributions of the anharmonic scatterings are evaluated numerically on the symmetry axes of aluminium and lead at room temperature. The observable asymmetries in the intensity distribution of the diffuse scatterings due to the anharmonic scattering are found near the reciprocal lattice points of the both crystals.