title: Ab initio structure determination of the hygroscopic anhydrous form of alpha-lactose by powder X-ray diffraction.
abstract: Annealing of alpha-lactose monohydrate at 408 K yielded a mixture of this compound with hygroscopic anhydrous alpha-lactose. A powder X-ray diffraction pattern of this mixture was recorded at room temperature. The starting structural model of hygroscopic alpha-lactose was found by a Monte Carlo simulated-annealing method. The final structure was obtained through Rietveld refinements, with soft restraints on interatomic bond lengths and bond angles, and crystalline energy minimization to locate the H atoms of the hydroxy groups. The crystalline cohesion is achieved by networks of O-H...O hydrogen bonds that differ from those of the monohydrate phase. The width of the Bragg peaks is interpreted by a phenomenological microstructural approach in terms of isotropic size effects and anisotropic strain effects.
authors.affiliation: Laboratoire de Dynamique et Structure des Matériaux Moléculaires (UMR CNRS 8024), UFR de Physique, Bâtiment P5, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cédex, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Platteau
authors.forename: Jacques
authors.initials: J
authors.lastname: Lefebvre
authors.forename: Frederic
authors.initials: F
authors.lastname: Affouard
authors.forename: Patrick
authors.initials: P
authors.lastname: Derollez
mesh_terms: D006860:Hydrogen Bonding; D007785:Lactose / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011208:Powders; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D011208:Powders; D007785:Lactose