[gmx-users] Center of mass drift in interfacial systems.

[Justin Lemkul]

On 12/10/12 5:18 AM, Anders Lervik wrote:
> Dear all,
>
> I have been simulating an inhomogeneous system consisting of a membrane and
> a solvent (e.g a lipid bilayer solvated in water). In these simulations, I
> have noticed lateral movement in the COMs of the membrane and solvent -
> they move in opposite directions such that the overall center of mass of
> the system is fixed. A bit of reading on this mailing list tells me that I
> should reset the center of mass of the membrane and solvent separately to
> avoid this.
>
> I just wonder what the cause of the lateral drift/movement is? Is it a
> general "feature" of interfacial systems?
>
>

It's certainly normal behavior.  I think Erik hints at the origin of this 
phenomenon here:

http://lists.gromacs.org/pipermail/gmx-users/2005-October/017439.html

If there is no inherent XY friction, then the molecules will move rather freely 
according to their diffusion constants, which for water molecules and lipids 
would be quite different.

-Justin

-- 
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Justin A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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