Short answer -- use a dispersion correction if the force field was parameterized to include one. Make sure you use the cutoff that the lipid was parameterized for as well.
Long answer -- neither on nor off is correct for a lipid bilayer. A dispersion corrections corrects for the fact that you are neglecting the r^-6 term at long range. However, it assumes an isotropic distribution outside the cutoff. Lipid bilayers have long range order, so a standard dispersion correction is inappropriate. The lipid properties will be cutoff dependent, which is not a very good thing. See PJ in't Veld, AE Ismail, GS Grest, J. Chem. Phys. 127, 144711 (2007) for a solution, using Ewald summation for the Lennard-Jones terms. This is in the works for Gromacs (and has been for a while), but might still be a while because it's a little lower on the to do list. Once methods like this are in, it will be possible to parameterize lipids that behave correctly. Best, Michael On Sun, Aug 19, 2012 at 3:16 PM, David Ackerman <da...@cornell.edu> wrote: > Hello, > > I was wondering when it is appropriate to use Dispersion Correction > for lipid bilayers, or which setting (no, EnerPres, or Ener) is best. > I have seen it used in some discussions, and not used in others. As > for myself, I have simulated a DPPC bilayer. With DispCorr=EnerPres, I > get an area per lipid of ~.615 nm^2 (whereas other reported values are > closer to .64 nm^2) and slower diffusion than is reported. However, > when I don't have a DispCorr term, my area per lipid becomes ~.656 > nm^2 and my diffusion more closely matches other reported values. > > So, should DispCorr be used at all for bilayer simulations, and if so, > which type is most appropriate? > > Thank you for your help, > David > -- > gmx-users mailing list gmx-users@gromacs.org > http://lists.gromacs.org/mailman/listinfo/gmx-users > * Only plain text messages are allowed! > * Please search the archive at > http://www.gromacs.org/Support/Mailing_Lists/Search before posting! > * Please don't post (un)subscribe requests to the list. Use the > www interface or send it to gmx-users-requ...@gromacs.org. > * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists -- gmx-users mailing list gmx-users@gromacs.org http://lists.gromacs.org/mailman/listinfo/gmx-users * Only plain text messages are allowed! * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/Search before posting! * Please don't post (un)subscribe requests to the list. Use the www interface or send it to gmx-users-requ...@gromacs.org. * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists
