[gmx-users] Surface tension

[Ganesh Shahane]

Thank you Andre. Your explanation answers my question very well.

On Tue, May 10, 2016 at 10:31 PM, André Farias de Moura <moura at ufscar.br>
wrote:

> Hi Ganesh,
>
> as any other pressure-related property, surface tension values over narrow
> timescales are really noisy for systems in the range of nanometers
> (increasing area should reduce the fluctuation).
>
> If simulations last  long enough, average values should be OK (please mind
> that average values may be different from experimental values, unless your
> force field has been parametrized to reproduce surface tension itself,
> which is not the case for most force fields).
>
> I hope it helps
>
> Andre
>
> On Tue, May 10, 2016 at 3:14 PM, Ganesh Shahane <ganesh7shahane at gmail.com>
> wrote:
>
> > Dear Gromacs Users,
> >
> > I have been trying to calculate the surface tension of pure water in a
> > cubic box, in which a layer of water molecules (along the XY plane) is
> > surrounded by vacuum on either sides of the Z-direction. Towards this, I
> > did an NVT simulation and computed the surface tension using gmx energy
> > (Gromacs 5.1) and got the following results:-
> >
> >  1000.000000  891.987000
> >  1005.000000  -1404.097290
> >  1010.000000  946.841919
> >  1015.000000  2523.864014
> >  1020.000000  317.747986
> >  1025.000000  422.096313
> >  1030.000000  -1233.948364
> >  1035.000000  2187.071777
> >  1040.000000  -88.564178
> >  1045.000000  -981.897888
> >  1050.000000  -429.718262
> >  1055.000000  121.672829
> > .
> > .
> > .
> > .
> >
> > My question is are the figures obtained as above normal/correct? My
> concern
> > is mainly because of the wide fluctuations in these readings. Also, when
> > you report the value of surface tension, do you average the numbers
> across
> > all the frames?
> >
> > Any help would be appreciated.
> >
> > Thank you!
> >
> > --
> > Cheers!
> > Ganesh Shahane
> > --
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>
>
> --
> _____________
>
> Prof. Dr. André Farias de Moura
> Department of Chemistry
> Federal University of São Carlos
> São Carlos - Brazil
> phone: +55-16-3351-8090
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-- 
Best Regards,
Ganesh Shahane