Dear all, I see that issues concerning PME and particle insertions have been discussed before, and some issues were apparently resolved for the latest (5.1.2) version. However, I have noticed a strange thing when using TPI for inserting (tip3p) water in liquid water at 300 K and 1 atm; the distribution of DU using PME becomes very different from when using a plain cutoff. Using reaction field electrostatics on the other hand gives a distribution which looks essentially the same as for cutoffs. You can have a look at the distributions at: http://www.wohlert.se/insrun.png
The reported chemical potentials also differ; cutoff and RF give reasonable <mu>, but with PME they differ by an order of magnitude. I also tried using water at lower density where convergence shouldn't be an issue, and basically got the same effect: http://www.wohlert.se/insrun2.png I would of course expect some difference between PME and plain cutoffs, but this seems unreasonable to me. Or isn’t it? Any suggestion what’s going on would be appreciated! Regards, Jakob PS I use gmx 5.1.2, with 7000 tip3p water in cubic box, and the mdp file looks as below, with the only difference between the runs is that coulomb type is either cut-off, PME, or Reaction-field. integrator = tpi dt = 0.002 nsteps = 100000 comm_mode = Linear comm_grps = System nstcomm = 1 pbc = xyz nstlist = 1 ns_type = grid rlist = 1.2 cutoff-scheme = group coulombtype = Cut-off rcoulomb = 1.2 vdw-type = Cut-off rvdw = 1.2 epsilon-rf = 80 Tcoupl = berendsen tc-grps = System tau_t = 2.0 ref_t = 300 ld_seed = -1 Pcoupl = no -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to gmx-users-requ...@gromacs.org.
