Hello,
I would like to anneal a crystal from 300 K to 0 K, after equilibrating in NPT at 300 K. I have been able to gather from google searching previous lammps questions that the proper way or performing this is the following procedure.
fix 1 all npt temp 300.0 300.0 100.0 aniso 1.01235 1.01235 100.0
run
unfix 1
fix 2 all nve
fix 3 all viscous 10.0
run
Now, I don’t quite understand how I can specify the target temperature of the annealing procedure. Is there anyway for me to know beforehand how long I need to run in nve for me to reach 0 K, or would a better procedure here be
unfix1
fix 2 all nvt 300.0 0.0 100.0
run
Conor
Hello,
I would like to anneal a crystal from 300 K to 0 K, after equilibrating in
NPT at 300 K. I have been able to gather from google searching previous
lammps questions that the proper way or performing this is the following
procedure.
i strongly suggest that you also consult some text book for proper
understanding of the method.
fix 1 all npt temp 300.0 300.0 100.0 aniso 1.01235 1.01235 100.0
run
unfix 1
fix 2 all nve
fix 3 all viscous 10.0
run
Now, I don't quite understand how I can specify the target temperature of
the annealing procedure. Is there anyway for me to know beforehand how long
theoretically, you will never reach it. you will always remove a
fraction of the kinetic energy. same as with minimization, you need to
stop when the total energy doesn't change anymore beyond a given
threshold. when this is reached cannot be predicted, because it
depends on how much potential energy will overall be removed from the
system. but since you can make a good guess based on the behavior at
the beginning of the annealing. just write out regular restarts and
terminate the calculation when there is no more significant
improvement.
I need to run in nve for me to reach 0 K, or would a better procedure here
be
unfix1
fix 2 all nvt 300.0 0.0 100.0
run
no. you want to remove the most energy from the fastest moving atoms,
i.e. the ones that go down the steepest path, so they don't overshoot
too much. the purpose and function of fix nvt is very different.
axel.