The asymmetry of neutron powder diffraction peaks

Profile analysis methods used with neutron diffraction data from powder samples require a knowledge of the shape and position of individual peaks. Because of the finite aperture of the detector these peaks become increasingly asymmetric at smaller Bragg angles, becoming broadened and shifted from the true Bragg angle. These effects are considered in detail by deriving the intensity distribution resulting from the resolution function of the diffractometer and evaluating it for a number of sets of instrumental parameters. The results are compared to those calculated ignoring the asymmetry, and empirical functions are derived for the required correction factors.