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Re: [lammps-users] fix rigid/npt with triclinic
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Re: [lammps-users] fix rigid/npt with triclinic

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Sun, 27 Aug 2017 16:34:52 -0400

On Thu, Aug 24, 2017 at 3:15 PM, Wes Barnett <w.barnett@...6288.....> wrote:
fix rigid/npt has not yet been implemented to work with triclinic boxes in LAMMPS. I'm interested if any users or devs have any kind of implementation of this feature in their own code.

​since nobody has responded publicly, i'd like to add, that i am not aware that this is on the TODO list of any LAMMPS developer. i am copying Trung, who was involved in the nose-hoover based rigid body integrators.

you may look into the regular fix rigid integrators for inspiration.​ the code structure is very similar, watch out for differences in variable names.

I've got a system of 32 nanoparticles functionalized with polymer grafts. The NP's are each a collection of points where the center interacts with the system using lj/expand and the grafts are tethered to non-interacting points on the surface. The surface points and center of each nanoparticle compose a rigid body.

I'm interested in allowing the nanoparticles to pack efficiently in the periodic box. If isotropic pressure coupling is used, their movement is restricted. When I use anisotropic pressure coupling I can already see some changes in packing. We're thinking it would be worthwhile to explore using a triclinic box if there is an implementation available using fit rigid/npt.

​as a workaround, you may try the following (off the top of my head, check docs for details):

group none type 999
fix 1 all rigid/nvt ....
fix 2 none nph ... dilate none
fix_modify 2 press thermo_press




James "Wes" Barnett
Postdoctoral Research Scientist
Department of Chemical Engineering

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Dr. Axel Kohlmeyer  akohlmey@...12...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.