I'm trying to do a very simple task in LAMMPS by generating an fcc Ni
sample with periodic boundary conditions and trying to equilibriate it
at 300K, just to observe the atoms vibrating in about their equilibrium
positions in VMD. I'm reading in lattice coordinates from a data file,
then using "velocity create" and then "fix nvt". In the thermo dump the
temperature goes to values way higher than the intended 300K. My script
is as follows:
I'm guessing the temperature fluctuations are too big, and I'm not sure
how to control it. Any help would be appreciated. Thanks!
rather than guessing, you should talk to somebody local
that has experience in MD simulations and discuss this.
this is in no way a LAMMPS specific problem or
related to the way LAMMPS implements this model.
there are a number of possible reasons and they are
difficult to assess from remotely and much more time
consuming to convey in any case. and please keep in
mind, that a mailing list is no substitute for an adviser.
you are most welcome to discuss any LAMMPS
specific problems here, though.
Your fix nvt time constant is 100 in metal units
which is psecs. Which is far too long for typical
usage. Try a value of 0.1 (~100 timesteps).