Charge Transfer between Water Molecules As the Possible Origin of the Observed Charging at the Surface of Pure Water

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Authors

VÁCHA Robert MARSALEK Ondrej WILLARD A.P. BONTHUIS D.J. NETZ R.R. JUNGWIRTH Pavel

Year of publication 2012
Type Article in Periodical
Magazine / Source Journal of Physical Chemistry Letters
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://pubs.acs.org/doi/full/10.1021/jz2014852
Doi http://dx.doi.org/10.1021/jz20148521
Field Physical chemistry and theoretical chemistry
Keywords simple continuum model; shear surface; Gibbs dividing surface; water/vapor interface; hydrogen bonding asymmetry
Attached files
Description Classical molecular dynamics simulations point to an anisotropy of water–water hydrogen bonding at the water surface. Approaching from the gas phase, a region of primarily dangling hydrogens is followed by dangling oxygens before the isotropic bulk region. Using ab initio calculations, we translate this hydrogen bonding anisotropy to charge transfer between water molecules, which we analyze with respect to both instantaneous and averaged positions of the water surface. Similarly to the oil/water interface, we show that there is a region of small net negative charge extending 0.2 to 0.6 nm from the Gibbs dividing surface in the aqueous phase. Using a simple continuum model, we translate this charge profile to a zeta potential, which acquires for realistic positions of the shear surface the same negative sign as that observed experimentally, albeit of a smaller absolute value.
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