[lammps-users] thermostatting and barostatting rigid body simulation

Hello, Steve,

I'm trying to simulate a mixture of rigid bodies and flexible molecules.
I would like to know how the temperature and pressure could be controlled.
After searching the mailing list achieves, I know there are some tricky ways
to do that, e.g. coupling the rigid bodies to a Langevin thermostat or simply
let the rest of the system taking the role as a thermostat.

I still have some questions:

1. Can I use "temp/rescale" or "temp/Berendsen" for thermostatting and
use "Press/Berendsen" for barostatting the rigid body system?

2. Does the total pressure reported by thermo command include the
contributions of rigid body to rigid body interaction and the interaction
between a rigid body and other soft molecules? (Or can this value be regarded
as the true pressure and be compared with experimental data?)

3. How can I control the pressure if the answer for the 1st question is no?
(Or is that possible currently?)

4. How can I thermostat or barostat if I use fix_poems? According to
lammps doc, it seems no way.:frowning:

I found in the mailing list, some other users have also similar questions. However
the answers are not very clear to me. Considering the decency of lammps, I would
like to recommend some papers (check out the attachments) to the author(s)
which are about the thermostatting or barostatting rigid body systems. They
are physically sound to me. I would like to know if they are worth being implemented
in lammps.


Rigid-body dynamics in the isothermal-isobaricensemble.pdf (166 KB)

Partial rigid-body dynamics in NPT, NPAT and NPT ensemblesfor proteins and membranes.pdf (279 KB)

Langevin thermostat for rigid body dynamics.pdf (759 KB)

A Rigid-Body-Based Multiple Time Scale Molecular DynamicsSimulation of Nanophase Materials.pdf (167 KB)

I've never tried to barostat a collection of rigid bodies. Currently
the only thermostat I know works is fix langevin as you mention.
The system pressure does include the rigid body contribution.

Currently, I have some code from Tony Sheh (U Michigan) to
do better thermo/baro statting of rigid bodies. We'll likely
release it in the next couple weeks. So I would wait and try
that to see if it works for you.