view article
Figure 6
Iterative SP-FFT phase refinement procedure for powder data. Only the differences with respect to the already described S-FFT algorithm are indicated (Fig. 3[link]). Initial phase values (upper right corner) are combined with weighted experimental and extrapolated amplitudes to give the initial ρ values (upper right corner). The Fourier coefficients of the [\delta _P^{\rm sq}] synthesis are obtained by combining the experimental (IH − 〈I〉) intensities with the ψ phases. The new structure factor estimates are alternatively obtained either by Fourier transforming δ·ρ (FT) or directly from the N top-ranked Fourier peaks (SFC) of δ·ρ. For overlapped reflections, [E_{\bf H}^2] values are updated every cycle [tH is the intensity redistribution coefficient calculated according to equation (33)[link], which ensures the constancy of the global cluster intensity].

IUCrJ
Volume 1| Part 5| August 2014| Pages 291-304
ISSN: 2052-2525
doi:10.1107/S2052252514017606