Secondary extinction in large single crystal

Universal expressions for the secondary extinction factor in ray and neutron crystallography were developed using three dimensionless parameters. The basis was an exact solution of the power transfer equations for the reflecting power (reflectivity) of a plane mosaic crystal. As a demonstration of the feasibility of these expressions, the problem of diffraction in a large lithium fluoride single crystal, which had been debated for a long time, was reanalyzed using Lawrence's data set and including all the hitherto omitted strong reflections (Y down to 0.20). The obtained value of R factor is less than 0.014.