Hello Users,
I’m attempting to model a couple polymer chains to see how they are packing. I know my starting configuration is far from equilibrium so I’m using an NPT ensemble:
fix 1 all npt temp 300.0 300.0 100.0 iso 1.0 1.0 1000.0
My pressure is jumping around pretty wildly. I’ve tried playing around with pdamp, setting it shorter (100) and longer (10000) but that didn’t seem to help. I’ve also tried messing around with drag, pchain, ploop and nreset but I haven’t been able to stabilize the pressure.
Any hints or tips would be awesome.
Thanks for your help,
Casey
Hello Users,
I'm attempting to model a couple polymer chains to see how they are
packing. I know my starting configuration is far from equilibrium so I'm
using an NPT ensemble:
fix 1 all npt temp 300.0 300.0 100.0 iso 1.0 1.0 1000.0
My pressure is jumping around pretty wildly. I've tried playing around with
pdamp, setting it shorter (100) and longer (10000) but that didn't seem to
help. I've also tried messing around with drag, pchain, ploop and nreset
but I haven't been able to stabilize the pressure.
a) what do you consider "wildly" ?
pressure fluctuations _are_ large for incompressible media
b) how large is your system.
pressure fluctuations get smaller with larger systems
c) how far is your system away from equilibrium?
have you considered running nvt (or even better nve + langevin)
for a while to dissipate the worst thermal fluctuations first?
please also have a look into the mailing list archives.
this question, i.e., what is a large fluctuation has been
discussed a lot and you should first figure out, whether
you are trying the impossible.
axel.