Dynamic characterization of crystalline and glass phases of deuterated 1,1,2,2 tetrachloroethane

作者：Perez Silvina C^*; Zuriaga Mariano; Serra Pablo; Wolfenson Alberto; Negrier Philippe; Lluis Tamarit Josep

来源：Journal of Chemical Physics, 2015, 143(13): 134502.

DOI：10.1063/1.4931824

A thorough characterization of the gamma, beta, 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 beta phase. In the beta phase, and from MDS, these reorientations are attributed to two possible movements, i.e., a 180 degrees reorientation around the C-2 molecular symmetry axis and a reorientation of the molecule between two non-equivalent positions. In the glass phase, the spin-lattice relaxation time T-1 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 beta-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.

• 出版日期2015-10-7