title: Dynamic characterization of crystalline and glass phases of deuterated 1,1,2,2 tetrachloroethane.
abstract: A thorough characterization of the γ, β, and glass phases of deuterated 1,1,2,2 tetrachloroethane (C2D2Cl4) via nuclear quadrupole resonance and Molecular Dynamic Simulations (MDSs) is reported. The presence of molecular reorientations was experimentally observed in the glass phase and in the β phase. In the β phase, and from MDS, these reorientations are attributed to two possible movements, i.e., a 180°  reorientation around the C2 molecular symmetry axis and a reorientation of the molecule between two non-equivalent positions. In the glass phase, the spin-lattice relaxation time T1 is of the order of 16 times lower than in the crystalline phase and varies as T(-1) below 100 K in good agreement with the strong quadrupolar relaxation observed in amorphous materials and in the glassy state of molecular organic systems. The activation energy of molecular reorientations in the glass phase (19 kJ/mol) is comparable to that observed in the glassy crystal of a "molecular cousin" compound, Freon 112 (C2F2Cl4), for the secondary β-relaxation. Moreover, the on-site orientational motion of tetrachloroethane molecules offers a new indirect evidence of the prominent role of such orientational disorder in glassy dynamics.
authors.affiliation: Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba and IFEG-CONICET, Ciudad Universitaria, X5016LAE Córdoba, Argentina.
authors.forename: Silvina C
authors.initials: SC
authors.lastname: Pérez
authors.affiliation: Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba and IFEG-CONICET, Ciudad Universitaria, X5016LAE Córdoba, Argentina.
authors.forename: Mariano
authors.initials: M
authors.lastname: Zuriaga
authors.affiliation: Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba and IFEG-CONICET, Ciudad Universitaria, X5016LAE Córdoba, Argentina.
authors.forename: Pablo
authors.initials: P
authors.lastname: Serra
authors.affiliation: Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba and IFEG-CONICET, Ciudad Universitaria, X5016LAE Córdoba, Argentina.
authors.forename: Alberto
authors.initials: A
authors.lastname: Wolfenson
authors.affiliation: Université Bordeaux, LOMA, UMR 5798, F-33400 Talence, France and LOMA, UMR 5798, F-33400 Talence, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Negrier
authors.affiliation: Grup de Caracterització de Materials, Departament de Física i Enginyeria Nuclear, ETSEIB, Diagonal 647, Universitat Politècnica de Catalunya, 08028 Barcelona, Catalonia, Spain.
authors.forename: Josep Lluis
authors.initials: JL
authors.lastname: Tamarit