On possibilities of double-crystal and triple-crystal X-ray diffractometry for studying monocrystal disordered surface layer structure

Results of double and triple-crystal X-ray diffractometry (TRD) for studying both ideal monocrystals and that with disordered surface layer are compared. Possibility of separating extremely weak coherent component of diffraction curves (DRC) at the background of intensive diffuse scattering is shown. The law of changing double-crystal DRC may be violated even when appreciable diffuse scattering in a sample is absent, that is related to the pseudopeak anomalous angular dependence on TRD spectra