The RED extinction model. I. An upgraded formalism
J. Kulda · Acta Crystallographica Section A Foundations of Crystallography · 1988
Some modifications are introduced into the extinction correction formulae based on the RED (random elastic deformation) model developed earlier by the author [Kulda (1987). Acta Cryst. A43, 167-173]. The scattering cross section, which includes a correction for primary extinction, has been extended to allow for a more general angular variation of the effective deformation gradient. The originally proposed cos θ dependence is included as one of the limiting cases corresponding to a pure lattice-plane misorientation. A modified expression has been derived for the angular reflection curve profile which describes properly the broadening due to the finite dimensions of the diffracting region. This version of the RED model containing three free parameters has been employed in experimental tests reported in paper II [Kulda (1988). Acta Cryst. A44, 286-290].