Energy flow of Bloch waves in X-ray dynamical diffraction in the Laue case for perfect crystals

The direction of energy flow for Bloch waves during X-ray dynamical diffraction in perfect crystals is investigated. The energy flow is spread uniformly within the Borrmann fan in the conventional Laue case where the imaginary part of the crystal structure factor is much smaller than the real part. However, when the imaginary part is large, as in the case of X-rays with energies close to the absorption edge for single atoms in crystals, the energy flow direction is found to be restricted, and the results are discussed in relation to the Bragg case.