We developed a method capable of solving ab initio complex crystal structures which contain individual atoms and/or highly flexible molecular fragments. The method employs a global optimisation technique and a versatile description of flexible molecular moieties in terms of stereochemical descriptors (bond lengths, bond angles and torsion angles) The power of the method was first demonstrated by solving the previously unknown crystal structure of (CH₂CH₂O)₃:LiN(SO₂CF₃)₂ (Andreev YG, Lightfoot P, Bruce PG. "Structure of the polymer electrolyte poly(ethylene oxide)₃: LiN(SO₂CF₃)₂ determined by powder diffraction using a powerful Monte Carlo approach" Chem. Comm.(18): 2169-2170 SEP 21 1996):  

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     A detailed description of the simulated annealing method can be found in Andreev YG, Lightfoot P, Bruce PG. A general Monte Carlo approach to structure solution from powder-diffraction data: Application to poly(ethylene oxide)₃:LiN(SO₂CF₃)₂ J. Appl. Crystallogr. 30: 294-305 Part 3 JUN 1 1997.

     The method has revolutionised the field of structure determination from powders and a number of complex crystal structures have been solved since its introduction. The structure of the most complex solid to be solved by powder diffraction (CH₂CH₂O)₆:LiAsF₆, with 50 atoms belonging to three separate moieties in the asymmetric unit and 79 variables (including 15 torsion angles) has been determined. (MacGlashan GS, Andreev YG, Bruce PG. Structure of the polymer electrolyte poly(ethylene oxide)₆:LiAsF₆ Nature 398 792-794 29 April 1999)

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Solving Structures of Crystalline Polymer Electrolytes Using a Combination of Single Crystal and Powder Diffraction

     Overlap of powder diffraction peaks coupled with the complexity of the structures sometimes precludes unambiguous structure determination from powder diffraction data alone, even by such a powerful method as simulated annealing. However, some of the polymer electrolyte structures can be successfully solved using our approach of combining the results of structure determination obtained by single crystal diffraction (from a complex prepared with a low-molecular-weight polymer), with the structure refinement by the Rietveld method of the powder diffraction data (from a complex prepared with a high-molecular-weight polymer). For the first time this method was successfully applied to (CH₂CH₂O)₈:NaBPh₄ (Staunton E, Christie AM, Andreev YG, Slawin AMZ, Bruce PG "The structure of poly(ethylene oxide)₈ : NaBPh₄ from a single crystal oligomer and polycrystalline polymer" Chem. Comm.(2): 148-149 2004):
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