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Simulating Surfactant-Iron Oxide Interfaces: From Density Functional Theory to Molecular Dynamics

preprint
submitted on 26.06.2019, 09:37 and posted on 26.06.2019, 14:29 by Carlos Ayestaran Latorre, James Ewen, Chiara Gattinoni, Daniele Dini
Understanding the behaviour of surfactant molecules on iron oxide surfaces is important for many industrial applications. Molecular dynamics (MD) simulations of such systems have been limited by the absence of a force-feild (FF) which accurately describes the molecule-surface interactions. In this study, interaction energies from density functional theory (DFT) + U calculations with a van der Waals functional are used to parameterize a classical FF for MD simulations of amide surfactants on iron oxide surfaces. The Original FF, which was derived using mixing rules and surface Lennard-Jones (LJ) parameters developed for nonpolar molecules, were shown to signi cantly underestimate the adsorption energy and overestimate the equilibrium adsorption distance compared to DFT. Conversely, the Optimized FF showed excellent agreement with the interaction energies obtained from DFT calculations for a wide range of surface coverages and molecular conformations near to and adsorbed on a-Fe2O3(0001). This was facilitated through the use of a Morse potential for strong chemisorption interactions, modi fied LJ parameters for weaker physisorption interactions, and adjusted partial charges for the electrostatic interactions. The Original FF and Optimized FF were compared in classical nonequilibrium molecular dynamics (NEMD) simulations of amide molecules con fined between iron oxide surfaces. When the Optimized FF was employed, the amide molecules were pulled closer to the surface and the orientation of the headgroups was more similar to that observed in the DFT calculations compared to the Original FF. The Optimized FF proposed here facilitates classical MD simulations of amide-iron oxide interfaces in which the interactions are representative of accurate DFT calculations.

Funding

EPSRC Centre for Doctoral Training in Theory and Simulation of Materials

Engineering and Physical Sciences Research Council

Find out more...

Afton Chemical Corp.

EPSRC EP/N025954/1

EPSRC EP/P030211/1

History

Email Address of Submitting Author

j.ewen@imperial.ac.uk

Institution

Imperial College London

Country

UK

ORCID For Submitting Author

0000-0001-5110-6970

Declaration of Conflict of Interest

None

Version Notes

First revision after submission

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