[lammps-users] rigid particles and fix langevin

Hi all,

I'm having a consistent problem in trying to run a Brownian Dynamics simulation of rigid particles on the order of 10 atoms. Basically after fixing the rigid bodies, i then apply:

fix integrator all nve
fix thermostat all langevin 1.000000 1.000000 1.000000 48279

as the simulation runs, the temperature drops from 1.0 to close to zero. I have used neigh_modify to turn off the force calculations between atoms within a rigid body. Basically, the simulation is not maintaining temperature. I have varied the damping coefficient from 1 to 2000 to no avail. Any suggestions on how to solve this problem?

Thanks in advance!
Tony Sheh

Hi Tony,

you only need to specify nve integrator for the flexible part, if any, of the system. The fix_rigid command already does the integration for rigid parts.


Quoting Tony Sheh <[email protected]>:

If you have a background solvent, then you do only want
to apply Langevin to the solvent, and also integrate the
solvent only with NVE. As the other responder mentioned,
you don't want to integrate the rigid atoms with both
nve and fix/rigid.

If you don't have a solvent, you need to think what is
the "temperature" of a set of rigid bodies and insure LAMMPS
is computing what you think it should be.