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Title: Role of quantum fluctuations in structural dynamics of liquids of light molecules

A possible role of quantum effects, such as tunneling and zero-point energy, in the structural dynamics of supercooled liquids is studied by dielectric spectroscopy. Our results demonstrate that the liquids, bulk 3-methyl pentane and confined normal and deuterated water, have low glass transition temperature and unusually low for their class of materials steepness of the temperature dependence of structural relaxation (fragility). Although we do not find any signs of tunneling in the structural relaxation of these liquids, their unusually low fragility can be well described by the influence of the quantum fluctuations. Confined water presents an especially interesting case in comparison to the earlier data on bulk low-density amorphous and vapor deposited water. Confined water exhibits a much weaker isotope effect than bulk water, although the effect is still significant. Here, we show that it can be ascribed to the change of the energy barrier for relaxation due to a decrease in the zeropoint energy upon D/H substitution. We observed a difference in the behavior of confined and bulk water demonstrates high sensitivity of quantum effects to the barrier heights and structure of water. Moreover, these results demonstrate that extrapolation of confined water properties to the bulk water behavior ismore » questionable.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry and Joint Inst. for Neutron Sciences
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
  3. Arizona State Univ., Tempe, AZ (United States). School of Molecular Sciences
  4. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry and Joint Inst. for Neutron Sciences and Dept. of Physics and Astronomy
  5. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725; CHE-1213444
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 145; Journal Issue: 23; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS
OSTI Identifier:
1347332