Mixing entropy. The mixing entropy of a POPE/POPC (3:1) bilayer over 200 ns, scaled such that S
=1. The bilayer is initialised such that POPC lipids (shown in red) encompass the lower left quadrant of the bilayer and the remaining bilayer contains POPE lipids (shown in green), creating a perfectly demixed system. An initial entropy of 0.3 is observed, which increases as the lipid types mix together. By 150 ns, the resulting entropy settles just below the theoretical maximum entropy, indicating a perfectly mixed system.