Dear,
All time related observables have to scaled by a factor
of 4 in the CG. This was originaly derived from the
diffusion porperties of Water an lipids. You've found it
by
yourself on the water diffusion.
XAvier
-----------------
XAvier Periole
MD-Group
University of Groningen
The Netherlands.
-----------------
I am trying to get my feet wet with the Coarse-grained
Force Field
developed by Marrink et al.
I've downloaded the examples of top-File, gro-file and
mdp-file for the
Water model on Marrink's website.
Unfortunately, I didn't succeed to reproduce the
diffusion constant and
isothermal compressibility data found in Marrink's
paper:
"Coarse-grained Model for Semi-Quantitative Lipid
Simulations", J. Phys.
Chem. B, 2004, 108, 750-760.
The gro-file contains 1728 W beads.
I didn't changed the parameters in the mdp-file: 100000
time Steps of 50
fs.
From g_energy, I obtained an isothermal compressibility
of 1.25x10-5 bar-1
instead of 6x10-5 bar-1 found by Marrink.
From g_msd, I obtained a diffusion constant of 1.5x10-5
cm2/s instead of
5x10-6 cm2/s found by Marrink.
The Coarse-grained diffusion constant has to be multiply
by 4 (a CG Water
bead representing 4 Water molecule) in order to obtained
a real diffusion
constant of 2x10-5 cm2/s...
Do you have any idea why I am not able to reproduce
Marrink's data?
Thank you for your help
Best Regards
Pierre Verstraete
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