Crystal structure prediction for six monosaccharides revisited

Six monosaccharides were studied as prototypes for flexible molecules, form ing crystal structures with complex hydrogen bond patterns. In earlier work the prediction of these crystal structures had been attempted using empiri cal force fields. Now ab initio energies have been calculated for 20 hypoth etical structures of each substance, along with corrections to the free ene rgy at room temperature. Five experimental structures corresponded to the g lobal free energy minimum, the sixth ranking second at a relative free ener gy of only 1.3 kJ/mol. This strongly suggests that a thermodynamic approach to crystal structure prediction will often be adequate, kinetic effects be ing dominant only in a minority of cases.