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Evolution from Surface-Influenced to Bulk-Like Dynamics in Nanoscopically Confined Santiago Romero-Vargas Castrilln,

Summary: Evolution from Surface-Influenced to Bulk-Like Dynamics in Nanoscopically Confined
Santiago Romero-Vargas Castrillón,
Nicola´s Giovambattista,
Ilhan A. Aksay,
Pablo G. Debenedetti*,
Department of Chemical Engineering, Princeton UniVersity, Princeton New Jersey 08544-5263, and
Physics Department, Brooklyn College of the City UniVersity of New York, Brooklyn, New York 11210
ReceiVed: March 20, 2009; ReVised Manuscript ReceiVed: April 29, 2009
We use molecular dynamics simulations to study the influence of confinement on the dynamics of a nanoscopic
water film at T ) 300 K and F ) 1.0 g cm-3
. We consider two infinite hydrophilic ( -cristobalite) silica
surfaces separated by distances between 0.6 and 5.0 nm. The width of the region characterized by surface-
dominated slowing down of water rotational dynamics is 0.5 nm, while the corresponding width for
translational dynamics is 1.0 nm. The different extent of perturbation undergone by the in-plane dynamic
properties is evidence of rotational-translational decoupling. The local in-plane rotational relaxation time
and translational diffusion coefficient collapse onto confinement-independent "master" profiles as long as the
separation d g 1.0 nm. Long-time tails in the perpendicular component of the dipole moment autocorrelation
function are indicative of anisotropic behavior in the rotational relaxation.


Source: Aksay, Ilhan A. - Department of Chemical Engineering, Princeton University


Collections: Materials Science