Methods for the Correction of X-Ray Intensities for Primary and Secondary Extinction in Crystal Structure Analysis

Abstract

The theory of x‐ray extinction in diffraction studies is reviewed, and application to small crystals completely bathed in the incident beam is considered. Using a suitable approximation to a sum of Bessel functions, a correction formula is obtained, valid in the region of small Bragg angle θ where the extinction is likely to be greatest. The formula is discussed; and it is shown that when the crystal structure is essentially known, as in later stages of refinement, it is possible to separate the effects of primary from secondary extinction and to correct the experimental data accordingly.