Dynamics of the Water Molecules at the Intrinsic Liquid Surface As Seen from Molecular Dynamics Simulation and Identification of Truly Interfacial Molecules Analysis
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Dynamic properties at the liquid-vapor interface of water are investigated at 298 K on the basis of molecular dynamics simulations and intrinsic surface analysis. The mean surface residence time and diffusion coefficient of the molecules as well as H-bond lifetimes are calculated at the liquid surface and compared to the bulk values. It is found that surface molecules have a non-negligible diffusion component along the surface normal, although this component is limited in time to 7-15 ps, a value comparable with the mean surface residence time. It is also seen that interfacial molecules move considerably faster, and their H-bonds live shorter, than in the bulk liquid phase. This finding is explained by the relation between the number of H-bonded neighbors and mobility, namely that molecules being tethered by more H-bonds move slower, and their H-bonds live longer than in the case of molecules of less extensive H-bonding. Finally, it is found that molecules residing long at the surface ...are clustering around each other, forming more and longer living H-bonds within the surface layer, but much less outside this layer than other interfacial molecules, indicating that longer surface residence is related to weaker interaction with the subsurface region.
Source:Journal of Physical Chemistry. C, 2016, 120, 16, 8578-8588
- Hungarian OTKA Foundation [104234, 119732]