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Re: [lammps-users] Adjusting pressure
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Re: [lammps-users] Adjusting pressure


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Thu, 28 Sep 2017 17:30:27 -0400



On Thu, Sep 28, 2017 at 3:09 AM, Omar Khalil <omaralkhalil88@...24...> wrote:
Dear all,

I have a system containing water molecules confined between two parallel solid walls. I want to move the walls in the perpendicular direction (z) to adjust the initial pressure to a specific value. How can I do it? 
It should be noted that I am using pppm algorithm with slab correction and so due to non-periodic condition in z direction, I cant use NPT ensemble.

​you *can* use fix​
​ npt for as long as you only couple the box change to x and y and keep z unchanged, which is probably the simplest way to equilibrate your system to the desired total pressure/density.

please note that there is a significant different between _using fix npt_ and _running in the NPT ensemble_.
you will *only* run in NPT ensemble​ if you use fix npt *and* have a fully periodic system without walls and other fixes that manipulate the system.

​axel.​

 

Best wishes,
Omar

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--
Dr. Axel Kohlmeyer  akohlmey@...12...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.