Dear all,
I’m simulating the diffusion process of interstitial atoms to a defects sink, which is included in an inner block region (‘side in’). I intend to add interstitial atoms in the surrounding region randomly during MD simulation, but don’t know how to realize it. I’ve tried ‘fix gcmc’ but it seems not support for ‘side out’ region, and the command ‘create atoms random’ created high energy configurations and leaded to runtime errors.
It’s there any other LAMMPS commands can realize my purpose?
Dear all,
I’m simulating the diffusion process of interstitial atoms to a
defects sink, which is included in an inner block region (‘side in’). I
intend to add interstitial atoms in the surrounding region randomly during
MD simulation, but don’t know how to realize it. I’ve tried ‘fix gcmc’ but
it seems not support for ‘side out’ region,
fix gcmc (and any other facility using regions) does not know anything
about side in or side out. the region class instances return a yes/no
answer for whether an atom is inside or outside the defined region to any
caller.
a way to place atoms and avoid the high energy issues due to random
placement would be to use a simple "soft" potential for the new atoms and
then fix adapt to gradually grow the interaction, so that those added atoms
can smoothly "unoverlap" before switching to the real potential.
axel.
axel.
Do you mean fix gcmc can be used with side out region? But I found the manual said “This command may optionally use the region keyword to define an exchange and move volume. The specified region must have been previously defined with a region command. It must be defined with side = in.’ and when I used fix gcmc with ‘side out’ , something like:
region MC block 4 14 3 12 4 18 side out
fix 1 all gcmc {Interval_run} 1 0 2 {seed} {tem} {miu} ${dis} region MC
an error message appeared:
ERROR: Fix gcmc region does not support a bounding box
Do you mean fix gcmc can be used with side out region? But I found the
manual said “This command may optionally use the region keyword to
define an exchange and move volume. The specified region must have been
previously defined with a region command. It must be defined with side =
in.’ and when I used fix gcmc with ‘side out’ , something like:
region MC block 4 14 3 12 4 18 side out
fix 1 all gcmc \{Interval\_run\} 1 0 2 {seed} \{tem\} {miu} ${dis}
region MC
an error message appeared:
ERROR: Fix gcmc region does not support a bounding box
you are correct and i was wrong. fix gcmc is special and uses (for
efficiency reasons) information about a region that most parts of LAMMPS
do not use when accessing a region.
axel.
that still leaves the option to keep your lattice atoms immobile and just insert atoms at random positions and then “unoverlap” them using a soft potential before switching to a regular potential.
axel.