hi,
we are doing an npt run on an energy minimized box of an ionic liquid pair, we fixed the carbon-hydrogen bonds in the energy minimization bonds using very high bond coefficients. while running the npt run, on the energy minimized box we are getting very high negative pressure can you suggest any fixes to properly run the npt simulation?
please find attached our input files for the npt run [in.nick3] and the input data file of run [minimized_constrained.out] and the log file.
Thank you,
Granite Tait
in.nick3 (1.06 KB)
log.lammps (2.7 KB)
minimized_constrained.out (8.93 KB)
hi,
we are doing an npt run on an energy minimized box of an ionic liquid pair, we fixed the carbon-hydrogen bonds in the energy minimization bonds using very high bond coefficients. while running the npt run, on the energy minimized box we are getting very high negative pressure can you suggest any fixes to properly run the npt simulation?
you have a tiny system, any attempt to run in parallel is a waste of time.
also, you have no initial temperature assigned.
the pressure is actually not that large for such a tiny system and it is missing the kinetic contribution due to 0K on the first step.
it is not a very smart idea, to start such a system with NPT. as has been discussed on this list many, many times, nose-hoover thermostats and barostats are not a good choice to equilibrate systems that are far from equilibrium. it is much better to use a dissipative thermostat and first run with a fixed volume before applying a barostat. for initial adjustment, fix press/berendsen is much more effective. make sure, that you don’t use too short a time constant, as that will lead to instabilities, especially for such a tiny system and the resulting large pressure fluctuations.
axel.