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Entropy Evaluation of the Superprotonic Phase of CsHSO_4: Pauling’s Ice Rules Adjusted for Systems Containing Disordered Hydrogen-Bonded Tetrahedra

Chisholm, Calum R. I. and Haile, Sossina M. (2007) Entropy Evaluation of the Superprotonic Phase of CsHSO_4: Pauling’s Ice Rules Adjusted for Systems Containing Disordered Hydrogen-Bonded Tetrahedra. Chemistry of Materials, 19 (2). pp. 270-279. ISSN 0897-4756. https://resolver.caltech.edu/CaltechAUTHORS:20131125-162531297

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Abstract

The entropy of the superprotonic transition (phase II → phase I) of CsHSO₄ is evaluated both experimentally and theoretically. Calorimetric measurements reveal a value of 14.75(22) J mol⁻¹ K⁻¹. Under the assumption that the entropy is entirely configurational, arising from both sulfate group orientational disorder and disorder in the hydrogen-bond network, we evaluated several structural models of CsHSO₄ for their consistency with the measured entropy. For a structure in which hydrogen-bond disorder is independent of sulfate-group orientational disorder, simple methods of calculating the number of structural configurations are inadequate. Thus, the configurational entropy of the superprotonic, disordered phase of CsHSO₄ is evaluated using an approach similar to that employed by Pauling to describe the residual entropy of ice at 0 K. Analogous to ice and the so-called ice rules, superprotonic CsHSO₄ is assumed to obey a set of structural rules. Key among these are that there is only one proton per sulfate tetrahedron and only one proton per hydrogen bond. Defects are argued to make a negligible contribution to the transition entropy. The transition entropy obtained from this model, 14.9 J mol⁻¹ K⁻¹, is in excellent agreement with the measured value. Such a match between theoretical and experimental values suggests that of all published Phase I structures, the structure proposed by Jirak² more correctly describes the arrangements of the sulfate tetrahedra and protons attached to them. The assumption of a low defect concentration implies that the jump in proton conductivity at the transition is due to an increase in the mobility of charge carriers rather than their concentration.


Item Type:Article
Related URLs:
URLURL TypeDescription
http:/dx.doi.org/10.1021/cm062070wDOIArticle
http://pubs.acs.org/doi/abs/10.1021%2Fcm062070wPublisherArticle
ORCID:
AuthorORCID
Haile, Sossina M.0000-0002-5293-6252
Alternate Title:Entropy Evaluation of the Superprotonic Phase of CsHSO4: Pauling’s Ice Rules Adjusted for Systems Containing Disordered Hydrogen-Bonded Tetrahedra
Additional Information:Copyright © 2007 American Chemical Society. Received August 31, 2006. Revised Manuscript Received October 26, 2006. Publication Date (Web): December 24, 2006. CM062070W. The authors thank Dr. Jeff Snyder and Dr. Dane Boysen for insightful discussions. This work has been supported by the National Science Foundation, DMR-0435221, and by the Donors of the American Chemical Society Petroleum Research Fund.
Funders:
Funding AgencyGrant Number
NSFDMR-0435221
American Chemical Society Petroleum Research FundUNSPECIFIED
Subject Keywords:fuel-cell electrolytes superionic phase neutron-diffraction high-temperature dielectric relaxations dihydrogen phosphates electrical-conduction proton conductivity sulphuric acid transitions
Issue or Number:2
Record Number:CaltechAUTHORS:20131125-162531297
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131125-162531297
Official Citation:Entropy Evaluation of the Superprotonic Phase of CsHSO4:  Pauling's Ice Rules Adjusted for Systems Containing Disordered Hydrogen-Bonded Tetrahedra. Calum R.I. Chisholm and and Sossina M. Haile. Chemistry of Materials 2007 19 (2), 270-279.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42712
Collection:CaltechAUTHORS
Deposited By: Jonathan Gross
Deposited On:27 Nov 2013 19:46
Last Modified:03 Oct 2019 06:01

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