The bending rigidity of an amphiphilic bilayer from equilibrium and nonequilibrium molecular dynamics

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Helfrich's theory predicts that the bending free energy of a tensionless amphiphilic bilayer is proportional to the square of the Fourier coefficients of the undulation modes. Equilibrium molecular dynamics simulations with coarse-grained amphiphiles confirm the correctness of this prediction for thermally excited undulations. The proportionality constant then provides the bending rigidity of the layer. Non-equilibrium methods, in particular umbrella sampling, potential of mean constraint force, and thermodynamic integration in Cartesian coordinates, have been used to extend the range of sampled amplitudes. For small amplitudes there is a good agreement with the equilibrium simulations, while beyond the thermally accessible amplitudes a clear deviation from theory is observed. Calculations of the elastic modulus showed a pronounced system size dependence.
Original languageUndefined
Pages (from-to)4712-4720
Number of pages9
JournalThe Journal of chemical physics
Issue number10
Publication statusPublished - 2003


  • METIS-213084
  • IR-59935

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