[gmx-users] Questions on surface tension anaysis.

[Eric Jakobsson]

The units for surface tension are force/distance; i.e., it is the magnitude 
of the lateral force along an interface divided by the length over which 
the force acts.

Within a molecular dynamics calculation, it is the difference between the 
virial normal to the interface and the virial parallel to the interface 
integrated along the normal to the interface.

Eric

At 07:59 PM 10/24/2003 -0400, you wrote:
>The surface tension should have the same unit as pressure:Bar, why Bar*nm?
>
>
>
>Quoting Marcos Villarreal <arloa at dqb.fcq.unc.edu.ar>:
>
> > On Friday 24 October 2003 15:32, you wrote:
> > > Dear. gmx-users.
> > >
> > > I used g_energy with #surf*surften option to analyze surface tensions of
> > my
> > > monolayer systems. I got some results like below.
> > >
> > > Energy                      Average       RMSD     Fluct.      Drift
> > > Tot-Drift
> > >
> > ---------------------------------------------------------------------------
> > >---- 
> #Surf*SurfTen              -991.074    2303.49    2302.97  0.0206873
> >
> > > 169.84
> > >
> > > I couldn't understand my results because this number doesn't look like
> > what
> > > we expected. Also, I could see the graph, using xmgrace, but the unit was
> > > kJ/mol, which is not appropriate unit for surface tension.
> > >
> > > Therefore, I would like to know how those surface tension calculations
> > are
> > > done, and which units those values have...how to analyze those numbers...
> > >
> > > best,
> > > Hwankyu.
> >
> > the units in #Surf*SurfTen are Bar*nm which is an order of magnitude larger
> >
> > than the more commonly used mN/m.
> > Remember that "#Surf" stands for "number of surfaces"
> >
> > All graphs made by g_energy say E(kJ/mol). Even the temperature!
> >
> > Saludos,
> > --
> > Marcos Villarreal
> > Grupo de Biofisica
> > Departamento de Quimica Biologica - CIQUIBIC.
> > Universidad Nacional de Cordoba.
> > Cordoba. Argentina.
> > http://www.fcq.unc.edu.ar/ciquibic
> > _______________________________________________
> > gmx-users mailing list
> > gmx-users at gromacs.org
> > http://www.gromacs.org/mailman/listinfo/gmx-users
> > Please don't post (un)subscribe requests to the list. Use the
> > www interface or send it to gmx-users-request at gromacs.org.
> >
>
>
>_______________________________________________
>gmx-users mailing list
>gmx-users at gromacs.org
>http://www.gromacs.org/mailman/listinfo/gmx-users
>Please don't post (un)subscribe requests to the list. Use the
>www interface or send it to gmx-users-request at gromacs.org.

---------------------------------
Eric Jakobsson, Ph.D.
Professor, Department of Molecular and Integrative Physiology, and of 
Biochemistry
Senior Research Scientist, National Center for Supercomputing Applications
Professor, Beckman Institute for Advanced Science and Technology
4021 Beckman Institute, mc251
405 N. Mathews Avenue
University of Illinois, Urbana, IL 61801
ph. 217-244-2896       fax 217-244-2909

(Currently on leave to NIH to serve as Director of Center for 
Bioinformatics and Computational Biology at the National Institute of 
General Medical Sciences and Chair of the NIH Biomedical Information 
Science and Technology Initiative Consortium.  Usual schedule is four days 
a week at NIH and three days a week at Illlinois.)