The energy F depends on the distribution of water and lipid in space, 𝜙(r). 𝜙 2 (r) describes the local concentration of water at position r: at the center of the lipid bilayer, 𝜙(r) = 0, while positive and negative values of 𝜙 reflect the two disconnected networks of water channels, one on each side of the bilayer. The two water regions are physically equivalent, so the functional in Equation 3 must be an even function of 𝜙(r). We assume after previous work by Góźdź 𝑓[𝜙(r)] = (𝜙(r) 2 -1) 2 (𝜙(r)) and 𝑔[𝜙(r)] = 𝑔 2 𝜙(r) 2 + 𝑔 0 with g2 = 4.01 -g0 and g0 = -3.