Prediction of crystal structures of two monosaccharides by potential energy minimisation

Crystal structures of a monoclinic and a hexagonal munosaccharide, 40 atoms per molecule, were successfully predicted by a potential energy minimisati on method. The intermolecular interactions were described by three terms co vering electrostatic, attraction and repulsion contributions to the total e nergy. Two types of atomic charges based on the Hartree-Fock wave function, Mulliken and derived from the electrostatic field generated by a molecule, were combined with two forte fields called Williams and Dreiding. With the cell parameters fixed, the correct structure was found in approximately 75 % of cases. With the cell parameters optimised no reasonable structure was found for the hexagonal monosaccharide. The accuracy of the predicted struc tures was evaluated by means of X-ray Rietveld refinements.