Extending the S-FFT direct-methods algorithm to density functions with positive and negative peaks. XIV.

摘要: Some years ago the direct-methods origin-free modulus sum function (S) was adapted to processing of intensity data from density functions with positive and negative peaks [Rius, Miravitlles & Allmann (1996). Acta Cryst. A52, 634-639]. That implementation used phase relationships explicitly. Although successfully applied different situations where number reflections small, its generalization larger problems required avoiding time-consuming manipulation quartet terms. To circumvent this limitation, a modification recently introduced S-FFT algorithm (that maximizes S only Fourier transforms) is presented here. The resulting S2-FFT highly effective for crystal structures at least one moderate scatterer in unit cell. Test calculations have been performed on conventional single-crystal X-ray diffraction data, neutron compounds scatterers intensities superstructure solve difference structures.