Open AccessA molecular dynamics study of water mass accommodation on condensed phase water coated by fatty acid monolayers
Author(s) -
Takahama S.,
Russell L. M.
Publication year - 2011
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010jd014842
Subject(s) - molecular dynamics , chemical physics , monolayer , molecule , scattering , materials science , context (archaeology) , radiative transfer , myristic acid , chemistry , computational chemistry , fatty acid , organic chemistry , physics , nanotechnology , optics , palmitic acid , biology , paleontology
As the water uptake by particles and clouds influences the radiative balance of the Earth, it is desirable to understand the mechanisms and parameters, which regulate water uptake in these colloidal particles. In this work, molecular dynamics simulations were used to simulate scattering or accommodation of water vapor molecules impinging on a slab of water and slabs of water coated by monomolecular amphiphile films: octanoic acid (C 8 ) at surface densities of 29 and 18 Å 2 per molecule and myristic acid (C 14 ) at 29 Å 2 per molecule. The mass accommodation coefficient of near unity on a pure water slab is in agreement with values estimated using similar scattering simulations using other potentials for water. The addition of surface‐active organic molecules in quantities corresponding to less than 1% of mass in a typical cloud droplet are predicted to reduce this mass accommodation coefficient by 70–100% in similar types of scattering simulations. The mass accommodation coefficient decreased monotonically with projected surface coverage of the hydrocarbon backbones, although the accommodation mechanisms differed by packing density and type of organic molecule. The mechanisms of interaction of the impinging water vapor molecules with the simulated organic films are discussed in the context of their chemical characteristics and physical structures (e.g., fatty acid chain orientation).