Interfacial Water at Graphene Oxide Surface: Ordered or Disordered?

The graphene oxide water interface was simulated using Born-Oppenheimer molecular dynamics (BOMD) simulations with two different functionals, namely, revPBE-D3 and BLYP-D2 as well as a commonly used classical force-field, namely OPLS-AA. A number of different order parameters, including the orientation of the interfacial water molecules near the aromatic region of the GO surface as well as those near the oxygenated defects, were examined and compared. The BOMD interfacial waters are clearly much less structured as compared to the classical forcefield that shows a strongly ordered interface. Higher level calculations, namely SAPT, were carried out on representative clusters taken from the BOMD simulation. These calculations revealed not only that a number of conformations have similar interaction energies but also the importance of induction contribution to the interaction energies.