Quantitative phase determination from three-beam diffraction with a corrected scaling scheme

The scaling scheme in the quantitative phase-determination procedure proposed by Chang & Tang [Acta Cryst. (1988), A44, 1065-1072] is corrected by taking the average peak intensity of two centrosymmetrically related three-beam diffractions as the maximum kinematical intensity for the reconstruction of the phase-independent intensity profiles. By subtraction of these phase-independent profiles from the measured intensity distributions, more reliable information about phases can be obtained. This procedure is applied to the three-beam diffraction profiles of several organic crystals, reported by Hiimmer, Weckert & Bondza [Acta Cryst. (1990), A46, 393-402], for quantitative phase analysis. The determined phase values are in good agreement with those calculated from the known structures.