Steric Interactions in Multimembrane Systems: A Monte Carlo Study

Abstract
The out-of-plane fluctuations of fluid membranes are sterically hindered in multilayer systems. To leading order, the free energy of steric repulsion per unit area of membrane is ΔfN(d) = cN(kBT)2d2, where T is the temperature, χ the rigidity constant, d the mean membrane separation, and N the number of membranes in the stack. Improving an earlier Monte Carlo investigation by Janke and Kleinert, cN is determined for N = 1, 3, and 5. A novel method for extrapolating these data to N = ∞ is presented. Using this method, we estimate c ≈ 0.106, a result which casts some doubt on the applicability of the harmonic models currently used to analyse X-ray scattering experiments on swollen lyotropic lamellar phases.