Exploring Adsorption of Water and Ions on Carbon Surfaces using a Polarizable Force Field.

Graphene, carbon nanotubes, and fullerenes are of great interest due to their unique properties and diverse applications in biology, molecular electronics, and materials science. Therefore, there is demand for methods that can accurately model the interface between carbon surfaces and their environment. In this letter we compare results for complexes of water, potassium ion, and chloride ion with graphene, carbon nanotube, and fullerene surfaces using a standard non-polarizable force field (OPLS-AA), a polarizable force field (OPLS-AAP), DFT, and ab initio theory. For interactions with water, OPLS-AA with the TIP3P or TIP4P water models describes the interactions with benzene (C(6)H(6)) and coronene (C(24)H(12)) well; however, for acenes larger than circumcoronene (C(54)H(18)) and especially for C(60), the interaction energies are somewhat too weak and polarization is needed. For ions interacting with carbon surfaces, inclusion of polarization is essential, and OPLS-AAP is found to perform well in comparison to the highest-level quantum mechanical methods. Overall, OPLS-AAP provides an accurate and computationally efficient force field for modeling condensed-phase systems featuring carbon surfaces.