On 17 May 2012 05:10, Erik Marklund <er...@xray.bmc.uu.se> wrote: > > 17 maj 2012 kl. 05.00 skrev Juliette N.: > > Hello everyone, > > I am trying to estimate the thermodynamic expression, dP/dw at > constant V and T, for my polymer-solvent system. Where P is the > pressure, w is the mass fraction, V volume and T temperature. I guess > this task can not be done by MD, as for constant Volume, pressure is > meaningless. Since what g_energy reports is not the actual pressure > which corresponds to that fixed Volume. Am I correct? > > > Hi, I lost you there. Why is pressure meaningless at constant volume?
Thanks. Because in NVT pressure is not controlled by thermostat. I have seen this issue discussed many times on the list archive that in NVT pressure values has no significance. I have seen this myself in simulations too, when I fix the pressure by NPT, get the density corresponding to that P. But when creating a box size of that density and running NVT, the pressure that NVT produces is far away from what it should be (Sometimes large negative values). > > Best, > > Erik > > > (I mean building different binary systems with different mass > fractions of w, and measuring average P (dP/dw) while keeping T and V > constant does not produce meaningful results by MD) > > Please comment if this makes sense in MD or not. > > Thanks, > J. > -- > 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 > > > ----------------------------------------------- > Erik Marklund, PhD > Dept. of Cell and Molecular Biology, Uppsala University. > Husargatan 3, Box 596, 75124 Uppsala, Sweden > phone: +46 18 471 6688 fax: +46 18 511 755 > er...@xray.bmc.uu.se > http://www2.icm.uu.se/molbio/elflab/index.html > > > -- > 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 -- Thanks, J. N. -- 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
