Ab initio solution of a complex crystal structure from powder-diffraction data using simulated-annealing method and a high degree of molecular flexibility

Abstract

The previously unknown crystal structure of the polymer/salt complex poly(ethylene oxide):${\mathrm{NaSO}}_{3}$${\mathrm{CF}}_{3}$ was solved from a powder-diffraction pattern collected on a laboratory x-ray diffractometer. The solution was performed starting from a random arrangement of constituent molecular fragments in the unit cell using a full-profile-fitting technique and a simulated-annealing method for finding the global minimum of the figure-of-merit function. Unlike the only other structure solution using this approach, the procedure was successful only when the highest degree of flexibility was applied to stereochemically constrained species.