[lammps-users] Ion Implantation with Lammps


I would like to use Lammps so investigate ion implantation of H, Ar into
a Si wafer. When I use

  velocity Argon set 0 0 5 units box
  velocity Silicon create 200.00 2349852

to create the initial velocities and use the following fix to

      fix 3 Silicon nvt 300.00 300.00 0.018

the system temperature goes to zero after 2 steps and it never changes.
I have created two groups (Argon and Silicon at the beginning.

Any idea what I'm doing wrong?




That nvt control constant (Tdamp=0.018) seems awfully small. Note that Tdamp has units of time, so assuming you're using real units with a timestep of around a fs, you're asking LAMMPS to remove all excess energy within a small fraction of a timestep, which is not good. How about Tdamp=100 ?


If that doesn't help, you might also try running nve for a while to make sure things look good before turning on your nvt fix.

Good luck,


I would visualize the simulation and see if it does
what you think it is doing.