[gmx-users] External electric field applied to water box

Justin Lemkul jalemkul at vt.edu
Wed May 22 19:39:18 CEST 2019

On 5/22/19 1:34 PM, Alex wrote:
> To quickly chime in: we routinely use anisotropic coupling for 
> relaxation (constant box size in XY) without any issues. There is a 
> good reason for that in our case (an XY-membrane splitting the box 
> mid-Z, which we don't want to mangle). Again, no issues whatsoever. 
> Water is TIP4P in our case. I suspect issues with setup in your case.

That's a very different system than a box of pure water. If your XY size 
is fixed (essentially NPAT), is anistropic coupling even relevant or 
necessary? Membranes are classic semiisotropic systems, which you have 
by fixing the XY vectors, no?

I'm mostly curious about the setup. I used anisotropic coupling a long 
time for membranes and routinely observed square cross-sections become 
rectangular over 100 ns or so (not a big deal but still not really 
physically relevant) and I never see anyone doing membrane systems 
deviate from semiisotropic coupling, because it's the most intuitive.



Justin A. Lemkul, Ph.D.
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