Polymer Science Faculty Research


Molecular Dynamics Simulations of Halomethane Adsorption on Two Dissimilar Surfaces

Document Type


Publication Date

Spring 2010


In this study, atomic-scale MD simulations were used to study multilayer adsorption of three different halomethane compounds (CF4, CF3Cl and CF3Br) onto two different surfaces (graphite and hydroxylated alpha-quartz) to show how orientation, layer structure, packing and dynamics vary as a function of temperature and substrate surface characteristics. In this way, non-polar CF4 on hydroxylated alpha-quartz is shown to exhibit a highly ordered packing arrangement only weakly dependent on temperature variation. In contrast, interactions between polar adsorbate groups and hydroxyl groups on the surface give CF3Cl and CF3Br a very different layer structure at the surface. Analysis of the orientations of polar molecules in the first adsorbed layer shows a lightly ordered arrangement of dipoles, and residence time and dipole correlation calculations suggest that this ordering is subject to frequent shifts in orientation and position within the film.



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