I have run NPT simulations using isotropic and semiisotropic coupling with the same results. I have never done coupling in just one direction though, how do you do this?. I have never used Dispersion corrections. It seems to me that this would help, rather than hurt though since, as Aldi said, it will make the system closer to experimental values. I will give this a try and see what happens. My question still remains - why do NPT and NVT simulations give such different values for surface tension? Denny Frost
On Sat, Mar 12, 2011 at 6:40 AM, aldi asmadi <aldi.asm...@gmail.com> wrote: > David, > > I have a question that is still related to your reply. If the bulk > liquid NPT and the interfacial liquid-vapor NVT simulations are > performed using dispersion corrections to the pressure and energy, > while the intefacial liquid-liquid NPAT simulation don't use any > correction, can we say that all results are valid since we don't give > the same treatment for all systems? > > In the NPT and NVT calculations, we apply corrections in order to > reduce the discrepancy between the calculated and experimental > properties (say density and surface tension) as small as possible. > Here we have more confidence that our molecules in systems behave > accordingly judging from the macroscopic values we obtain. Meanwhile, > in the NPAT calculation, we don't use such correction meaning that the > property (say interfacial tension) is expected to deviate more from > the experimental value? This indicates that the system behaves > differently in comparison to the same simulation conducted with > correction? > > Many thanks, > Aldi > > > On Sat, Mar 12, 2011 at 11:44 AM, David van der Spoel > <sp...@xray.bmc.uu.se> wrote: > > On 2011-03-12 06.09, Denny Frost wrote: > >> > >> I am running MD simulations on Liquid/Liquid interfaces and measuring > >> the interfacial tension between them. I have found that the readings in > >> NVT simulations are close to experimental values, but have a lot of > >> variation. I run NPT simulations on the exact same system and find the > >> results show very little variation, but the values are far from > >> experimental results. Does anyone know why this happens? > >> > > Please be more specific. How do you do NPT simulations? This may > influence > > the result. To get good result I would suggest to do pressure coupling > only > > in the normal direction and to turn off dispersion corrections to the > > pressure. > > > > -- > > David van der Spoel, Ph.D., Professor of Biology > > Dept. of Cell & Molec. Biol., Uppsala University. > > Box 596, 75124 Uppsala, Sweden. Phone: +46184714205. > > sp...@xray.bmc.uu.se http://folding.bmc.uu.se > > -- > > gmx-users mailing list gmx-users@gromacs.org > > http://lists.gromacs.org/mailman/listinfo/gmx-users > > 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 > 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 >
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