HASSINE, Bacem Ben; NEGRIER, Philippe; BARRIO, Maria; MONDIEIG, Denise; MASSIP, Stéphane; TAMARIT, Josep Lluis

doi:10.1021/acs.cgd.5b00764

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HASSINE, Bacem Ben
Laboratoire Ondes et Matière d'Aquitaine [LOMA]
Laboratoire des Matériaux Composites céramiques et Polymères [Université de Sfax] [LaMaCoP]

NEGRIER, Philippe
Laboratoire Ondes et Matière d'Aquitaine [LOMA]

BARRIO, Maria
Departament de Fisica i Enginyeria Nuclear [UPC, Barcelone] [ETSEIB]

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Crystal Growth & Design. 2015, vol. 15, n° 8, p. 4149–4155

American Chemical Society

Résumé en anglais

The polymorphism of 1-adamantane-methanol C11H18O has been investigated by differential thermal analysis and single-crystal and powder X-ray diffraction. Below the melting temperature (389.5 ± 0.4 K), this compound exhibits an orthorhombic phase (phase I, Pnnm, Z = 12, Z′ = 1.5). The melting enthalpy was determined to be 20.5 ± 0.4 kJ mol−1, i.e., with an entropy change of (6.34 ± 0.13)R, which is much higher than the quoted value from Timmermans for the melting orientationally disordered phases (2.5R), thus supporting the orientationally ordered character of phase I. This orthorhombic phase I exhibits a statistical disorder of the hydrogen atom related to the oxygen atom, due to the position of one independent molecule on the mirror. At ca. 272 K, phase I transforms continuously through an order−disorder transition to a low-temperature monoclinic phase II (P21/n, Z = 12, Z′ = 3). The monoclinic and orthorhombic phases are related by a group−subgroup relationship, which perfectly agrees with the continuous character of the II to I transition. Moreover, by a convenient choice of an order parameter related to the continuous tilt of the c-axis, the critical exponent for this transition is found to be close to the theoretical prediction of the threedimensional Ising model (with a critical exponent of ca. 0.27).< Réduire

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Phase Transition in Hydrogen-Bonded 1‑Adamantane-methanol

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