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Quantum diffusion in liquid water from ring polymer molecular dynamics

Miller, Thomas F., III and Manolopolous, David E. (2005) Quantum diffusion in liquid water from ring polymer molecular dynamics. Journal of Chemical Physics, 123 (15). Art. No. 154504. ISSN 0021-9606. http://resolver.caltech.edu/CaltechAUTHORS:MILjcp05b

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Abstract

We have used the ring polymer molecular-dynamics method to study the translational and orientational motions in an extended simple point charge model of liquid water under ambient conditions. We find, in agreement with previous studies, that quantum-mechanical effects increase the self-diffusion coefficient D and decrease the relaxation times around the principal axes of the water molecule by a factor of around 1.5. These results are consistent with a simple Stokes-Einstein picture of the molecular motion and suggest that the main effect of the quantum fluctuations is to decrease the viscosity of the liquid by about a third. We then go on to consider the system-size scaling of the calculated self-diffusion coefficient and show that an appropriate extrapolation to the limit of infinite system size increases D by a further factor of around 1.3 over the value obtained from a simulation of a system containing 216 water molecules. These findings are discussed in light of the widespread use of classical molecular-dynamics simulations of this sort of size to model the dynamics of aqueous systems.


Item Type:Article
Additional Information:©2005 American Institute of Physics. Received 12 July 2005; accepted 23 August 2005; published 20 October 2005. We would like to thank Michiel Sprik for suggesting this study and Paul Madden for some helpful discussions. This work was supported by the U.S. Office of Naval Research under Contract No. N000140510460.
Subject Keywords:polymers, water, molecular dynamics method, liquid theory, liquid structure, self-diffusion, fluctuations, viscosity
Record Number:CaltechAUTHORS:MILjcp05b
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:MILjcp05b
Alternative URL:http://dx.doi.org/10.1063/1.2074967
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11040
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:24 Jun 2008
Last Modified:26 Dec 2012 10:08

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