Syntax:
fix ID group-ID wall/sph wallstyle args ...
xplane or yplane or zplane args = lo hi r0 D lo,hi = position of lower and upper plane (distance units, either can be NULL) r0 = cutoff distance from wall at which wall-particle interaction due to repulsive force is cut off (distance units) D = prefactor for repulsive force zcylinder args = radius r0 D radius = cylinder radius (distance units) r0 = cutoff distance from wall at which wall-particle interaction due to repulsive force is cut off (distance units) D = prefactor for repulsive force
Examples:
fix wallhi all wall/sph xplane NULL 5.0 0.0 0.012 4.0 fix zcyl all wall/sph zcylinde 0.1 0.012 4.0
LIGGGHTS vs. LAMMPS Info:
This command is not available in LAMMPS.
Description:
Bound the simulation domain with a flat wall that interacts with the atoms in the group by generating a force on the atom in a direction perpendicular to the wall. The force magnitude is given by Lennard-Jones potential:
r is the distance from the particle to the wall, and r0 is the cutoff distance at which the particle and wall no longer interact.
IMPORTANT NOTE: You must insure that r is always > 0 for all particles in the group, or LIGGGHTS will generate an error. This means you cannot start your simulation with particles at the wall position or with particles on the wrong side of the wall (r < 0). The force on the particle blows up as r -> 0. This means the initial particle spacing must be carefully choosen.
Restart, fix_modify, output, run start/stop, minimize info:
No information about this fix is written to binary restart files.
None of the fix_modify options are relevant to this fix.
No global scalar or vector or per-atom quantities are stored by this fix for access by various output commands.
No parameter of this fix can be used with the start/stop keywords of the run command.
This fix is not invoked during energy minimization.
Restrictions: none
Related commands:
Default: none