Figure provides snapshots of the bilayers at different 𝑎 𝐿 at temperatures 293 K, 304 K, and 324 K, while Figure depicts the corresponding membrane hydrophobichydrophilic interfacial tension 𝛾 𝐵𝐿 . As shown in Figure , bilayers can be compressed to negative surface tension values up to a point where deformation occurs. Negative surface tension indicates that the bilayer is overcompressed and tends to expand, leading to deformation. At this stage, the membrane area is no longer given by the lateral area of the simulation box. Figures and illustrate that both the deformation point and the extent of deformation are strongly temperaturedependent, and increase with temperature. Above the deformation point, the surface tension increases with area per lipid, nearly linear. However, below the main transition temperature 314 K, the tension area isotherm distinguishes the gel and liquid crystalline phases with different elastic responses, separated by the region of phase transition. In Figure , the bilayer with 𝑎 𝐿 = 52.6 𝐴 𝑜 2 at 293 K is in the gel phase, with high lipid order indicated by the red-colored tails. Further stretching leads to the formation of the liquid crystalline phase and eventually to completely disordered, thinner bilayers at high areas per lipid (see snapshot at 𝑎 𝐿 = 69. 7 𝐴 𝑜 2 ). Similarly, the bilayer with 𝑎 𝐿 = 55 Å 2 at 304 K is also in the gel phase, transitioning to the crystalline phase upon stretching. In Figure , the interfacial tension curves at 293 K and 304K consist of a cusp region, which indicates a first order transition. Such a phase transition region is absent in the curve at 324 K, as the bilayer is in the disordered liquid crystalline phase at all values of 𝑎 𝐿 (Figure ).