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

Justin Lemkul jalemkul at vt.edu
Mon Dec 10 15:13:08 CET 2012

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:


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 A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080


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