Coridan, Robert H. and Schmidt, Nathan W. and Lai, Ghee Hwee and Abbamonte, Peter and Wong, Gerard C. L. (2012) Dynamics of confined water reconstructed from inelastic x-ray scattering measurements of bulk response functions. Physical Review E, 85 (3). Art. No. 031501 . ISSN 1539-3755 http://resolver.caltech.edu/CaltechAUTHORS:20120413-105539692
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Nanoconfined water and surface-structured water impacts a broad range of fields. For water confined between hydrophilic surfaces, measurements and simulations have shown conflicting results ranging from “liquidlike” to “solidlike” behavior, from bulklike water viscosity to viscosity orders of magnitude higher. Here, we investigate how a homogeneous fluid behaves under nanoconfinement using its bulk response function: The Green's function of water extracted from a library of S(q,ω) inelastic x-ray scattering data is used to make femtosecond movies of nanoconfined water. Between two confining surfaces, the structure undergoes drastic changes as a function of surface separation. For surface separations of ≈9 Å, although the surface-associated hydration layers are highly deformed, they are separated by a layer of bulklike water. For separations of ≈6 Å, the two surface-associated hydration layers are forced to reconstruct into a single layer that modulates between localized “frozen’ and delocalized “melted” structures due to interference of density fields. These results potentially reconcile recent conflicting experiments. Importantly, we find a different delocalized wetting regime for nanoconfined water between surfaces with high spatial frequency charge densities, where water is organized into delocalized hydration layers instead of localized hydration shells, and are strongly resistant to `freezing' down to molecular distances (<6 Å).
|Additional Information:||© 2012 American Physical Society. Received 9 May 2011; revised manuscript received 10 January 2012; published 8 March 2012. G.W. was supported by the NSF RPI-UIUC NSEC. P.A. is supported by DOE Grants No. DEFG02-91ER45439 and No. DEFG02-07ER46459. We thank D. Chandler, K. Schweizer,M.Krisch, and D. Trinkle for insightful discussions and technical assistance.|
|Classification Code:||PACS: 61.20.-p, 34.50.-s, 68.08.Bc, 78.70.Ck|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||17 Apr 2012 18:23|
|Last Modified:||26 Dec 2012 15:03|
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