Diffuse scattering from crystals of glycolic acid

Abstract

Abstract From numerous experimental and theoretical studies of the thermal diffuse scattering of x-rays by molecular crystals, it follows that the loosely bound molecules in these crystals may undergo translational and librational oscillations as rigid units and as a result of this type of thermal motion a special kind of extended, continuous, diffuse scattering domains may appear in the diffraction pattern. A recent neutron crystal-structure analysis of glycolic acid suggests that the thermal motion in this crystal is of the type mentioned above. But the studies of the diffuse scattering pattern from the glycolic-acid crystal carried out in this work show that the extended, continuous, diffuse scattering domains that characterize this type of thermal motion are far too weak compared to their expected theoretical values as calculated on the basis of the thermal parameters evaluated by the method of crystal-structure analysis. A probable explanation is given for this disagreement between the experimental and theoretical results.