Solving crystal structures from powder data. V. Located molecular fragment and powder-pattern decomposition

In direct procedures for crystal structure solution from powder data, information on the location and orientation of a molecular fragment may readily become available. Such information may be used retrospectively to improve the powder-pattern decomposition, with favourable effects on the phasing process. A method is described by which accurate estimation of a large number of structure-factor moduli is possible by exploiting the prior partial structural information.