Density functional theory and molecular dynamics simulation of water molecules confined between two-dimensional graphene oxide surfaces

Abstract

In this work, the interaction potentials of water molecule with the two-dimensional graphene oxide (GO) surfaces containing epoxy groups have been determined using the M06–2X/6-31g (d,p) level of theory at different orientations and separations and fitted to the Born-Huggins-Meyer (BHM) potential. Good agreements were found between the computed and the well-known OPLS-AA and Dreiding potentials. We have also used some calculated potentials and the well-known models in the molecular dynamics (MD) simulations. Our results showed that some of the calculated force fields for both 2D GO structures almost represent similar results of average number of hydrogen bonds (<HB>), radial distribution functions (RDF), self-diffusion coefficient, and angle distribution function (ADF) with the OPLS-AA and Dreiding models which are due to their agreements of the interaction potentials. However, some models in both GO systems represent different results because of their shifted potentials to the larger distances. Our results also showed that the confined water molecules tend to orient toward the epoxy groups on the GO surfaces and the distributions at the angles of θ = 0^o (or θ = 180^o) is more than the other distributions. The water molecules confined between the bent GO surfaces showed less diffusion coefficients than the flat structure.