where L is the unit cell dimension (lattice parameter), and ϕ 2 (r) describes the concentration of water. At the centre of the bilayer, ϕ(r) = 0, and the aqueous regions in the two discrete continuous Furthermore, the energy of the (100) orientation is close to the bulk value for the bending energy of the 𝑄 𝐼𝐼 𝑃 phase of -0.181. This result indicates that a (100) interface of the form shown in Figure only adds a small energetic contribution, and therefore that it is unlikely that there exists some other interfacial orientation with lower energy than (100). We have used similar logic in our analysis of 𝑄 𝐼𝐼 𝐺 and 𝑄 𝐼𝐼 𝐷 orientation. Finally, the simulations confirm that the shape of the energy-minimised interface in Figure does indeed present a square array resembling the AFM image in Figure , with repeat spacing corresponding to the size of the 3D cubic unit cell.