Relaxation time and excess entropy in viscous liquids

Electric field versus temperature as control parameter

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7 Citations (Scopus)

Abstract

On the basis of adiabatic calorimetry data and results obtained from dielectric relaxation studies in the presence of a high static electric field, the effects of temperature and electric field induced changes of the excess entropy are compared for the same sample: supercooled cresolphthalein dimethylether. A field induced reduction of the excess entropy by 45 mJ K−1 mol−1 at constant temperature increases the structural relaxation time by 0.75%, while the same entropy change originating from lowering the temperature at constant field increases the time constant by 3.5%. Therefore, there is no simple link connecting excess entropy and relaxation time that is independent of the control parameter that is used to modify the entropy. A consequence is that the Adam-Gibbs approach does not provide a quantitative prediction for how the dynamics of liquids depend on the electric field, and, more generally, on excess entropy. This work compares the dynamics for temperature versus field induced changes of isobaric excess entropy, thereby eliminating previous uncertainties arising from isochoric versus isobaric conditions and from unknown relations between thermodynamic, excess, and configurational entropies.

Original languageEnglish (US)
Article number064501
JournalJournal of Chemical Physics
Volume146
Issue number6
DOIs
StatePublished - Feb 14 2017

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Relaxation time
Entropy
relaxation time
Electric fields
entropy
electric fields
Liquids
liquids
Temperature
temperature
Temperature distribution
temperature distribution
Structural relaxation
Dielectric relaxation
Calorimetry
time constant
heat measurement
Thermodynamics
thermodynamics
predictions

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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title = "Relaxation time and excess entropy in viscous liquids: Electric field versus temperature as control parameter",
abstract = "On the basis of adiabatic calorimetry data and results obtained from dielectric relaxation studies in the presence of a high static electric field, the effects of temperature and electric field induced changes of the excess entropy are compared for the same sample: supercooled cresolphthalein dimethylether. A field induced reduction of the excess entropy by 45 mJ K−1 mol−1 at constant temperature increases the structural relaxation time by 0.75{\%}, while the same entropy change originating from lowering the temperature at constant field increases the time constant by 3.5{\%}. Therefore, there is no simple link connecting excess entropy and relaxation time that is independent of the control parameter that is used to modify the entropy. A consequence is that the Adam-Gibbs approach does not provide a quantitative prediction for how the dynamics of liquids depend on the electric field, and, more generally, on excess entropy. This work compares the dynamics for temperature versus field induced changes of isobaric excess entropy, thereby eliminating previous uncertainties arising from isochoric versus isobaric conditions and from unknown relations between thermodynamic, excess, and configurational entropies.",
author = "Ranko Richert",
year = "2017",
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doi = "10.1063/1.4975389",
language = "English (US)",
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journal = "Journal of Chemical Physics",
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publisher = "American Institute of Physics Publising LLC",
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TY - JOUR

T1 - Relaxation time and excess entropy in viscous liquids

T2 - Electric field versus temperature as control parameter

AU - Richert, Ranko

PY - 2017/2/14

Y1 - 2017/2/14

N2 - On the basis of adiabatic calorimetry data and results obtained from dielectric relaxation studies in the presence of a high static electric field, the effects of temperature and electric field induced changes of the excess entropy are compared for the same sample: supercooled cresolphthalein dimethylether. A field induced reduction of the excess entropy by 45 mJ K−1 mol−1 at constant temperature increases the structural relaxation time by 0.75%, while the same entropy change originating from lowering the temperature at constant field increases the time constant by 3.5%. Therefore, there is no simple link connecting excess entropy and relaxation time that is independent of the control parameter that is used to modify the entropy. A consequence is that the Adam-Gibbs approach does not provide a quantitative prediction for how the dynamics of liquids depend on the electric field, and, more generally, on excess entropy. This work compares the dynamics for temperature versus field induced changes of isobaric excess entropy, thereby eliminating previous uncertainties arising from isochoric versus isobaric conditions and from unknown relations between thermodynamic, excess, and configurational entropies.

AB - On the basis of adiabatic calorimetry data and results obtained from dielectric relaxation studies in the presence of a high static electric field, the effects of temperature and electric field induced changes of the excess entropy are compared for the same sample: supercooled cresolphthalein dimethylether. A field induced reduction of the excess entropy by 45 mJ K−1 mol−1 at constant temperature increases the structural relaxation time by 0.75%, while the same entropy change originating from lowering the temperature at constant field increases the time constant by 3.5%. Therefore, there is no simple link connecting excess entropy and relaxation time that is independent of the control parameter that is used to modify the entropy. A consequence is that the Adam-Gibbs approach does not provide a quantitative prediction for how the dynamics of liquids depend on the electric field, and, more generally, on excess entropy. This work compares the dynamics for temperature versus field induced changes of isobaric excess entropy, thereby eliminating previous uncertainties arising from isochoric versus isobaric conditions and from unknown relations between thermodynamic, excess, and configurational entropies.

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