Simulation of multiple diffraction

The multiple diffraction of X-rays and neutrons is discussed on the basis of the kinematical theory; a program for the simulation of ψ scanning and λ scanning is developed, where the influence of the wavelength width of incident beams on the Ewald construction is properly taken into account. The effect of higher-order diffraction (n-beam interaction, n > 3) is treated as the sum of those of (n-2) pairs of relevant double diffractions (three-beam interactions). Applications are made for some examples for which experimental data are available; it is shown that the results are in very good agreement with experiment. This suggests that the kinematical approach is appropriate. The simulation is useful in planning ψ-scanning experiments for precise structure determination and for examining experimental data.