In Eq. ( ) 𝑃 𝑁 is the normal pressure, which is 𝑃 𝑧𝑧 , the normal component of the pressure tensor, and 𝑃 𝐿 is the lateral pressure, which is the average of the pressure tensor components in x and y directions. 𝐿 𝑧 is the length of the system in the normal direction and the factor 2 accounts for the existence of two monolayers in the simulaitons, which are in similar conditions. If 𝛾 0 is the surface tension of water at the air-water interface, without lipids, then the monolayer surface pressure is,