From: Jerome Henin (jerome.henin_at_uhp-nancy.fr)
Date: Fri Apr 08 2005 - 13:44:19 CDT
Hi Philip,
Actually, I did see a similar behaviour on some lipid bilayer I have simulated.
Until now, I assumed it to be a consequence of intrinsic properties of my
system, but I would be interested to know if many people experienced the same
situation, and if it somehow could be linked to the barostat.
Best,
Jerome
> I am equilibrating some lipid bilayer configurations (72 lipids) with a 
> fully flexible cell and I see something rather odd.  I start the 
> configurations at a higher area per lipid  than given by experiment and 
> I expect the bilayer to relax to a lower area per lipid, which it does.  
> The odd thing is that all the relaxation occurs in the x direction, 
> while the y dimension of the box stays at about the same average 
> length.  I realize that this could be a result of some weird thing with 
> the initial conditions, but I have seen this same behavior with two 
> separate configurations.
> 
> So I was wondering if those of you who have simulated lipid bilayers 
> with anisotropic pressure coupling or who have used anisotropic pressure 
> coupling in general could comment.  These are isotropic systems (in the 
> x-y plane), so it is strange that the cell would shrink over 8 angtroms 
> in the x direction and only 1 angstrom in the y direction (this is after 
> 10 ns of simulation time).  Could there be anything in the pressure 
> routine itself that might cause some bias?  Again I can't rule out that 
> this happens by chance, but it might be worthwhile to look into this.
> 
> Thanks,
> Phil Blood
> 
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