  Thermal diffuse scattering (TDS) caused by the interaction of high-energy
electrons with phonons has been investigated. An oscillating atom retains all
of its elastic scattering capacity, although the vibration changes the spatial
distribution of the scattering potential. Therefore, the scattering by the
vibrating lattice or phonons is still elastic. Furthermore, the TDS electrons
re-main coherent and form the diffuse interference patterns even under the
time-averaging assump-tion. Elastic and coherent TDS electrons contribute most
of the contrast of Kikuchi lines.
