Extended Data Figure 8: Van der Waals pressure acting on water trapped between graphene sheets.

a, Schematic illustration of water confined by graphene. Owing to adhesion between the graphene layers, water is squeezed into a 2D puddle. Parameters d and δ are used in our estimation of van der Waals pressure (see Methods). b, c, MD simulations of van der Waals pressure exerted on a gas bubble (1,000 He atoms) trapped between two freely moving graphene sheets, showing side (b) and top (c) views of the He nanoballoon. In b, the graphene layers are not shown for clarity, and in c they are in light grey. d–f, Simulations of 2D ice formed by a water nanodroplet (100 molecules) confined between two freely moving flexible graphene sheets. Oxygen atoms are shown in red, hydrogen in light grey and graphene in dark grey: side (d) and top (e, f) view at equilibrium Simulations in d and e were performed using the SPC/E model and, in f, using TIP4P/2005. For clarity, graphene is not shown in e and f. The lattice parameter in e and f is about 2.8 Å within the modelling accuracy.