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Liquid water is a dynamic polydisperse branched polymer

Naserifar, Saber and Goddard, William A., III (2019) Liquid water is a dynamic polydisperse branched polymer. Proceedings of the National Academy of Sciences of the United States of America, 116 (6). pp. 1998-2003. ISSN 0027-8424. PMCID PMC6369747. doi:10.1073/pnas.1817383116.

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We developed the RexPoN force field for water based entirely on quantum mechanics. It predicts the properties of water extremely accurately, with T_(melt) = 273.3 K (273.15 K) and properties at 298 K: ΔH_(vap) = 10.36 kcal/mol (10.52), density = 0.9965 g/cm³ (0.9965), entropy = 68.4 J/mol/K (69.9), and dielectric constant = 76.1 (78.4), where experimental values are in parentheses. Upon heating from 0.0 K (ice) to 273.0 K (still ice), the average number of strong hydrogen bonds (SHBs, r_(OO) ≤ 2.93 Å) decreases from 4.0 to 3.3, but upon melting at 273.5 K, the number of SHBs drops suddenly to 2.3, decreasing slowly to 2.1 at 298 K and 1.6 at 400 K. The lifetime of the SHBs is 90.3 fs at 298 K, increasing monotonically for lower temperature. These SHBs connect to form multibranched polymer chains (151 H₂O per chain at 298 K), where branch points have 3 SHBs and termination points have 1 SHB. This dynamic fluctuating branched polymer view of water provides a dramatically modified paradigm for understanding the properties of water. It may explain the 20-nm angular correlation lengths at 298 K and the critical point at 227 K in supercooled water. Indeed, the 15% jump in the SHB lifetime at 227 K suggests that the supercooled critical point may correspond to a phase transition temperature of the dynamic polymer structure. This paradigm for water could have a significant impact on the properties for protein, DNA, and other materials in aqueous media.

Item Type:Article
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URLURL TypeDescription Information CentralArticle
Naserifar, Saber0000-0002-1069-9789
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2019 National Academy of Sciences. Published under the PNAS license. Contributed by William A. Goddard III, December 17, 2018 (sent for review October 9, 2018; reviewed by Charles L. Brooks III and Michael L. Klein). PNAS published ahead of print January 24, 2019. We thank Dr. Sergey Zybin and Prof. Tod Pascal for helpful discussions. S.N. was supported by the Joint Center for Artificial Photosynthesis, a Department of Energy (DOE) Energy Innovation Hub, supported through the Office of Science of the US DOE under Award DE-SC0004993. W.A.G. was supported by the Computational Materials Sciences Program funded by the US DOE, Office of Science, Basic Energy Sciences, under Award DE-SC00014607. The calculations were carried out on the Extreme Science and Engineering Discovery Environment, which is supported by National Science Foundation Grant ACI-1548562. Author contributions: S.N. and W.A.G. designed research; S.N. performed research; S.N. and W.A.G. analyzed data; and S.N. and W.A.G. wrote the paper. Reviewers: C.L.B., University of Michigan; and M.L.K., Temple University. The authors declare no conflict of interest. This article contains supporting information online at
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Department of Energy (DOE)DE-SC00014607
Subject Keywords:water structure; molecular dynamics; liquid–liquid critical point; radial distribution function; density-functional theory
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Issue or Number:6
PubMed Central ID:PMC6369747
Record Number:CaltechAUTHORS:20190125-105921884
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Official Citation:Liquid water is a dynamic polydisperse branched polymer. Saber Naserifar, William A. Goddard. Proceedings of the National Academy of Sciences Feb 2019, 116 (6) 1998-2003; DOI: 10.1073/pnas.1817383116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92471
Deposited By: Tony Diaz
Deposited On:25 Jan 2019 19:57
Last Modified:01 Mar 2022 23:46

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