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Long-range effects of confinement on water structure
1Department of Chemistry, P.O. Box 30012, Texas A&M University, Texas 77843, USA.
The Journal of Physical Chemistry. B
|March 10, 2010
Summary
Water confined between hydrophobic surfaces shows unusual density and hydrogen bonding. Simulations reveal inhomogeneous water distribution and altered tetrahedrality, impacting hydration near surfaces.
Area of Science:
- Physical Chemistry
- Computational Nanoscience
Background:
- Understanding water behavior in confined spaces is crucial for nanotechnology and biological systems.
- Hydrophobic surfaces present unique challenges for water structuring and interactions.
Purpose of the Study:
- To investigate the structural and dynamic properties of water confined between hydrophobic surfaces using molecular dynamics simulations.
- To analyze the effects of confinement on water density, hydrogen bonding, and surface hydration.
Main Methods:
- Molecular dynamics simulations of water confined between planar or alkane monolayer hydrophobic surfaces.
- Analysis of water density distribution, hydrogen bond network, and tetrahedrality parameter (q).
- Validation using a free energy density functional approach.
Main Results:
- Inhomogeneous water density distribution with higher density near surfaces and lower density in the center at large separations (up to 800 A).
- Altered hydrogen bond network: more liquid-like near surfaces and more ice-like in the center.
- Confinement effects on water structure are largely independent of the specific hydrophobic model surfaces used.
- Minimal impact on water orientational relaxation dynamics.
Conclusions:
- Hydrophobic confinement significantly alters water's structure and density, creating long-range effects on its hydrogen bond network.
- The observed phenomena can be reproduced by free energy density functional theory with nonlocal terms.
- These findings provide insights into interfacial water behavior relevant to various scientific disciplines.
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