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Title: Observation of Fractional Stokes-Einstein Behavior in the Simplest Hydrogen-Bonded Liquid

Abstract

Quasielastic neutron scattering has been used to investigate the single-particle dynamics of hydrogen fluoride across its entire liquid range at ambient pressure. For T>230 K, translational diffusion obeys the celebrated Stokes-Einstein relation, in agreement with nuclear magnetic resonance studies. At lower temperatures, we find significant deviations from the above behavior in the form of a power law with exponent {xi}=-0.71{+-}0.05. More striking than the above is a complete breakdown of the Debye-Stokes-Einstein relation for rotational diffusion. Our findings provide the first experimental verification of fractional Stokes-Einstein behavior in a hydrogen-bonded liquid, in agreement with recent computer simulations [S. R. Becker et al., Phys. Rev. Lett. 97, 055901 (2006)].

Authors:
;  [1];  [2]; ;  [3];  [4]
  1. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)
  2. CSIC-Instituto Estructura de la Materia and Department of Electricity and Electronics, University Basque Country, P.O. Box 644, Bilbao 48080 (Spain)
  3. Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600 (United States)
  4. Spallation Neutron Source, Oak Ridge National Laboratory, Scarboro Road, Oak Ridge, Tennessee 37830 (United States)
Publication Date:
OSTI Identifier:
20955477
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 7; Other Information: DOI: 10.1103/PhysRevLett.98.077801; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 36 MATERIALS SCIENCE; COMPUTERIZED SIMULATION; HYDROFLUORIC ACID; HYDROGEN; LIQUIDS; NEUTRON REACTIONS; NUCLEAR MAGNETIC RESONANCE; QUASI-ELASTIC SCATTERING

Citation Formats

Fernandez-Alonso, F., McLain, S. E., Bermejo, F. J., Turner, J. F. C., Molaison, J. J., and Herwig, K. W. Observation of Fractional Stokes-Einstein Behavior in the Simplest Hydrogen-Bonded Liquid. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.077801.
Fernandez-Alonso, F., McLain, S. E., Bermejo, F. J., Turner, J. F. C., Molaison, J. J., & Herwig, K. W. Observation of Fractional Stokes-Einstein Behavior in the Simplest Hydrogen-Bonded Liquid. United States. doi:10.1103/PHYSREVLETT.98.077801.
Fernandez-Alonso, F., McLain, S. E., Bermejo, F. J., Turner, J. F. C., Molaison, J. J., and Herwig, K. W. Fri . "Observation of Fractional Stokes-Einstein Behavior in the Simplest Hydrogen-Bonded Liquid". United States. doi:10.1103/PHYSREVLETT.98.077801.
@article{osti_20955477,
title = {Observation of Fractional Stokes-Einstein Behavior in the Simplest Hydrogen-Bonded Liquid},
author = {Fernandez-Alonso, F. and McLain, S. E. and Bermejo, F. J. and Turner, J. F. C. and Molaison, J. J. and Herwig, K. W.},
abstractNote = {Quasielastic neutron scattering has been used to investigate the single-particle dynamics of hydrogen fluoride across its entire liquid range at ambient pressure. For T>230 K, translational diffusion obeys the celebrated Stokes-Einstein relation, in agreement with nuclear magnetic resonance studies. At lower temperatures, we find significant deviations from the above behavior in the form of a power law with exponent {xi}=-0.71{+-}0.05. More striking than the above is a complete breakdown of the Debye-Stokes-Einstein relation for rotational diffusion. Our findings provide the first experimental verification of fractional Stokes-Einstein behavior in a hydrogen-bonded liquid, in agreement with recent computer simulations [S. R. Becker et al., Phys. Rev. Lett. 97, 055901 (2006)].},
doi = {10.1103/PHYSREVLETT.98.077801},
journal = {Physical Review Letters},
number = 7,
volume = 98,
place = {United States},
year = {Fri Feb 16 00:00:00 EST 2007},
month = {Fri Feb 16 00:00:00 EST 2007}
}
  • Quasielastic neutron scattering has been used to investigate the single-particle dynamics of hydrogen fluoride across its entire liquid range at ambient pressure. For T > 230 K, translational diffusion obeys the celebrated Stokes-Einstein relation, in agreement with nuclear magnetic resonance studies. At lower temperatures, we find significant deviations from the above behavior in the form of a power law with exponent xi = -0.71+/-0.05. More striking than the above is a complete breakdown of the Debye-Stokes-Einstein relation for rotational diffusion. Our findings provide the first experimental verification of fractional Stokes-Einstein behavior in a hydrogen-bonded liquid, in agreement with recent computermore » simulations.« less
  • Kinetically constrained models have gained much interest as models that assign the origins of interesting dynamic properties of supercooled liquids to dynamical facilitation mechanisms that have been revealed in many experiments and numerical simulations. In this work, we investigate the dynamic heterogeneity in the fragile-to-strong liquid via Monte Carlo method using the model that linearly interpolates between the strong liquid-like behavior and the fragile liquid-like behavior by an asymmetry parameter b. When the asymmetry parameter is sufficiently small, smooth fragile-to-strong transition is observed both in the relaxation time and the diffusion constant. Using these physical quantities, we investigate fractional Stokes-Einsteinmore » relations observed in this model. When b is fixed, the system shows constant power law exponent under the temperature change, and the exponent has the value between that of the Frederickson-Andersen model and the East model. Furthermore, we investigate the dynamic length scale of our systems and also find the crossover relation between the relaxation time. We ascribe the competition between energetically favored symmetric relaxation mechanism and entropically favored asymmetric relaxation mechanism to the fragile-to-strong crossover behavior.« less
  • From temperature studies at ambient pressure, it was pointed out for several glass-forming liquids that the {alpha}-relaxation time ({tau}) can be related to the dc-ionic conductivity ({sigma}) through the phenomenological fractional Debye-Stokes-Einstein (DSE) equation. In the present paper we test the validity of fractional DSE equation for relaxation data obtained from pressure variable experiments. To this end we carried out broadband dielectric measurements (10 mHz{endash}10 MHz) in a wide range of pressures (0.1{endash}300 MPa). The material under study were N,N-diglycidyl-4-glycidyloxyaniline and N,N-diglycidylaniline. As a result we found that the fractional DSE equation is also obeyed for pressure pathways.
  • Be diffusivity data in the bulk metallic glass forming alloy Zr{sub 46.7}Ti{sub 8.3}Cu{sub 7.5}Ni{sub 10}Be{sub 27.5} are reported for temperatures between 530 and 710 K, extending 85 K into the supercooled liquid state of the alloy. At the glass transition temperature {ital T}{sub {ital g}}, a change in temperature dependence of the data is observed, and above {ital T}{sub {ital g}} the diffusivity increases more quickly with temperature than below. The data in the supercooled liquid can be described by a modified Arrhenius expression based on a diffusion mechanism suggested earlier. The comparison with viscosity data in the supercooled liquidmore » state of Zr{sub 46.7}Ti{sub 8.3}Cu{sub 7.5}Ni{sub 10}Be{sub 27.5} reveals a breakdown of the Stokes{endash}Einstein relation, indicating a cooperative diffusion mechanism in the supercooled liquid state of Zr{sub 46.7}Ti{sub 8.3}Cu{sub 7.5}Ni{sub 10}Be{sub 27.5}. {copyright} {ital 1996 American Institute of Physics.}« less
  • The Stokes-Einstein relation, relating the diffusion and viscosity coefficients D and {eta}, is tested in two dimensions. An equilibrium molecular-dynamics simulation was used with a Yukawa pair potential. Regimes are identified where motion is diffusive and D is meaningful. The Stokes-Einstein relation, D{eta}{proportional_to}k{sub B}T, was found to be violated near the disordering transition; under these conditions collective particle motion exhibits dynamical heterogeneity. At slightly higher temperatures, however, the Stokes-Einstein relation is valid. These results may be testable in strongly coupled dusty plasma experiments.