[gmx-users] surface tension

Jay Mashl mashl at uiuc.edu
Mon Jun 30 18:59:01 CEST 2003

On Thu, 7 Feb 2002, David van der Spoel wrote:

> Date: Thu, 7 Feb 2002 08:29:42 +0100 (CET)
> From: David van der Spoel <spoel at xray.bmc.uu.se>
> Cc: gmx-users at gromacs.org
> Subject: Re: [gmx-users] surface tension
> On Wed, 6 Feb 2002, paloureiro wrote:
> >is it possible to use the surface tension option with the Parrinello algorithm (the manual says it is not) ?
> >I have been using the surface-tension with the Berendsen p couple in a DPPC bilayer, but my system behaves in a strange way:
> >the use of -200 bar.nm or +200 bar.nm leads to a contraction in the XY plane (I would expect -200 bar.nm to contract and +200 bar.nm to expand the xy area).
> >I have used either cut-off and PME electrostatics. I have set the compressibility to 9.8e-5 bar-1 in  xy and z.
> >
> >Any suggestion will be very helpful.
> I don't know whether something could be wrong with the algorithm, but I
> suggest you check the initial conditions: run without P coupling and
> measure the pressure (average over > 100 ps). Chances are that your
> pressure is very negative already, so the system should contract. Also,
> since your compressibility is low you will have only small differences in
> area with -200 and +200 bar. Measure (using g_energy) the area and surface
> tension after quilibration and then compare again.

I would like to reiterate the first question asked:  Is the Parrinello
algorithm (offically) supported for use with surface tension coupling, despite
the manual stating otherwise?  The source code for versions 3.1.4 and cvs seem
to support this combination.


Computational Biology
National Center for Supercomputing Applications
University of Illinois

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