The bending modulus is an important physical constant characterizing
lipid membranes. Different methods have been devised for calculating
the bending modulus from simulations, and one of them, named the buckling
method, is nowadays widely used due to its simplicity and numerical
stability. However, questions remain on the reproducibility, finite
size effects, and interpretation of results on lipid mixtures. Here
we explore the dependence of simulation results on the system size
and the strain. We find that the dimensions of the box have a negligible
impact on the results when the system size is beyond a certain threshold.
We then calculate the bending rigidity for of a series of common single-component
lipid bilayers (PC, PS, PE, PG, and SM), as well as a number of binary
and ternary lipid mixtures. We find that bending moduli of lipid mixtures
can be predicted from the weighted average of the moduli of the individual
components, as long as the mixture is homogeneous. For phase-separated
mixtures, the apparent elastic modulus is closer to the value of the
softer component. Predictions of the bending modulus based on the
area compressibility modulus are found to be generally unreliable.
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