[gmx-users] Surface Tension Calculation

David van der Spoel spoel at xray.bmc.uu.se
Fri Sep 15 06:10:57 CEST 2006

toma0052 wrote:
> Hi,
>      I posted a question a few days ago regarding the calculation of the
> surface tension of a lipid bilayer in Gromacs.  The response that I got was
> to use the option "#Surf*SurfTens" in g_energy.  I am not really sure how
> to do this.  I have looked at the g-energy file in Gromacs, and I don't see
> any option that is "#Surf*SurfTens".  Maybe the file name is wrong, or I am
> running an older version of Gromacs or something.  Let me know if is there
> is a way to calculate the surface tension of a lipid bilayer within the
> Gromacs program, or if it is necessary for me to modify the code.  (The
> more detailed the better. I am new to Gromacs)
yes, print the diagonal terms of the pressure tensor, and assuming you 
surface is normal to the Z-axis you have
gamma = (Pzz - (Pxx+Pyy)/2) / Lz
where Lz is the box length. If you have two surfaces you have to divide 
by two.
> Thanks,
> Mike Tomasini
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David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se

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