Orientational relaxations in solid (1,1,2,2)tetrachloroethane
| Autor: | Michela Romanini, Roberto Macovez, J. Ll. Tamarit, Pablo Serra, Efstratia Mitsari, Pragya Tripathi, Mariano Zuriaga |
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| Přispěvatelé: | Universitat Politècnica de Catalunya. Departament de Física, Universitat Politècnica de Catalunya. GCM - Grup de Caracterització de Materials |
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
010304 chemical physics
Física [Àrees temàtiques de la UPC] Chemistry Relaxation (NMR) General Physics and Astronomy 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Tetrachloroethane Chemistry Physical and theoretical Anàlisi espectral Molecular dynamics Dipole Nuclear magnetic resonance Molecular solid Chemical physics Phase (matter) 0103 physical sciences Molecular symmetry Intermediate state Physical and Theoretical Chemistry 0210 nano-technology Fisicoquímica |
| Zdroj: | UPCommons. Portal del coneixement obert de la UPC Universitat Politècnica de Catalunya (UPC) Recercat. Dipósit de la Recerca de Catalunya instname |
| Popis: | We employ dielectricspectroscopy and molecular dynamic simulations to investigate the dipolar dynamics in the orientationally disordered solid phase of (1,1,2,2)tetrachloroethane. Three distinct orientational dynamics are observed as separate dielectric loss features, all characterized by a simply activated temperature dependence. The slower process, associated to a glassytransition at 156 ± 1 K, corresponds to a cooperative motion by which each molecule rotates by 180° around the molecular symmetry axis through an intermediate state in which the symmetry axis is oriented roughly orthogonally to the initial and final states. Of the other two dipolar relaxations, the intermediate one is the Johari-Goldstein precursor relaxation of the cooperative dynamics, while the fastest process corresponds to an orientational fluctuation of single molecules into a higher-energy orientation. 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 their collective motion. These findings show that the combination of dielectricspectroscopy and molecular simulations allows studying in great detail the orientational dynamics in molecular solids. |
| Databáze: | OpenAIRE |
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