First-principles simulation of water on graphene using different levels of theory

We show results from molecular-dynamics simulations of water confined between flat graphene sheets using different levels of theory. DFT simulations using PBE exchange-correlation show strong layering near the graphene sheet, with the hydrogens closer to the graphene surface. Correlations die off to bulk values after $\sim $10{\AA} from the surface. Inclusion of an empirical Grimme-type van der Waals potential has a small effect on the interfacial C-H distance but a seemingly large effect from the second coordination shell onwards from the surface. Existing reactive force-fields for water, e.g. ReaxFF, do not capture the structure of water on graphene accurately and require refitting to more closely reproduce the DFT results. Molecular dynamics results with available self-consistent vDW-DFx kernels and contrasts with existing classical water models will also be presented.