IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
artículos
Título:
Orientational relaxations in solid (1,1,2,2)tetrachloroethane
Autor/es:
E. MITSARI; J. LL. TAMARIT; P. TRIPATHI; P. SERRA; M. ROMANINI; R. MACOVEZ; M J ZURIAGA
Revista:
JOURNAL OF CHEMICAL PHYSICS
Editorial:
AMER INST PHYSICS
Referencias:
Lugar: New York; Año: 2016 vol. 144 p. 1645051 - 1645057
ISSN:
0021-9606
Resumen:
We employ dielectric spectroscopy and molecular dynamic simulations to investigate the dipolardynamics in the orientationally disordered solid phase of (1,1,2,2)tetrachloroethane. Three distinctorientational dynamics are observed as separate dielectric loss features, all characterized by asimply activated temperature dependence. The slower process, associated to a glassy transition at156 ± 1 K, corresponds to a cooperative motion by which each molecule rotates by 180◦ aroundthe molecular symmetry axis through an intermediate state in which the symmetry axis is orientedroughly orthogonally to the initial and final states. Of the other two dipolar relaxations, the intermediateone is the Johari-Goldstein precursor relaxation of the cooperative dynamics, while thefastest process corresponds to an orientational fluctuation of single molecules into a higher-energyorientation. The Kirkwood correlation factor of the cooperative relaxation is of the order of one tenth,indicating that the molecular dipoles maintain on average a strong antiparallel alignment during theircollective motion. These findings show that the combination of dielectric spectroscopy and molecularsimulations allows studying in great detail the orientational dynamics in molecular solids