title: Growth-induced incommensurability observed in the organic co-crystal hexamethylenetetramine resorcinol.
abstract: Co-crystals of hexamethylenetetramine and resorcinol were investigated by X-ray diffraction. The structure was refined in the superspace group Xmcm(0beta0)s0s, X=(1/2 1/2 0 1/2). In the average structure the resorcinol molecules are disordered between two orientations. The main effect of the modulation in the structure is a harmonic modulation of the occupation probabilities of the two orientations of the resorcinol molecule. However, the modulated order is not perfect and the resorcinol molecules remain partially disordered. Below 270 K the crystal undergoes a phase transition to a commensurately modulated structure with modulation vector q=(0 1/2 1/4) and superspace group X2/m(0betagamma)0s. The structure of the low-temperature phase could not be determined owing to the poor quality of the crystals affected by the reconstructive phase transition.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Cristallographie, BSP, CH-1015 Lausanne, Switzerland.
authors.forename: Soraya Maria Belluga
authors.initials: SM
authors.lastname: Rodriguez
authors.forename: Lukás
authors.initials: L
authors.lastname: Palatinus
authors.forename: Václav
authors.initials: V
authors.lastname: Petrícek
authors.forename: Gervais
authors.initials: G
authors.lastname: Chapuis
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008709:Methenamine / Q000737:chemistry*; D008958:Models, Molecular; D012118:Resorcinols / Q000737:chemistry*; D013696:Temperature
chemical_list: D012118:Resorcinols; D008709:Methenamine; C031389:resorcinol