lammps/doc/fix_wall_lj93.txt

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fix wall/lj93 command :h3

[Syntax:]

fix ID group-ID wall/lj93 style coord epsilon sigma cutoff :pre

ID, group-ID are documented in "fix"_fix.html command
wall/lj93 = style name of this fix command
style = {xlo} or {xhi} or {ylo} or {yhi} or {zlo} or {zhi}
coord = position of wall
epsilon = Lennard-Jones epsilon for wall-particle interaction
sigma = Lennard-Jones sigma for wall-particle interaction
cutoff = distance from wall at which wall-particle interaction is cut off :ul

[Examples:]

fix wallhi all wall/lj93 xhi 10.0 1.0 1.0 2.5 :pre

[Description:]

Bound the simulation domain with a Lennard-Jones wall that encloses
the atoms.  The energy E of a wall-particle interactions is given by
the 9-3 potential

:c,image(Eqs/fix_wall_lj93.jpg)

where {r} is the distance from the particle to the wall {coord}, and
epsilon and sigma are the usual LJ parameters.  Rc is the cutoff value
specified in the command.  This interaction is derived by integrating
over a 3d half-lattice of Lennard-Jones 12-6 particles.  A harder,
more repulsive wall interaction can be computed by using the "fix
wall/lj126"_fix_wall_lj126.html command.

The wall potential is shifted so that the energy of a wall-particle
interaction is 0.0 at the cutoff distance.

[Restart, fix_modify, output, run start/stop, minimize info:]

No information about this fix is written to "binary restart
files"_restart.html.

The "fix_modify"_fix_modify.html {energy} option is supported by this
fix to add the energy of interaction between atoms and the wall to the
system's potential energy as part of "thermodynamic
output"_thermo_style.html.

This fix computes a scalar energy and a 3-vector of forces (on the
wall), which can be accessed by various "output
commands"_Section_howto.html#4_15.

No parameter of this fix can be used with the {start/stop} keywords of
the "run"_run.html command.

The forces due to this fix are imposed during an energy minimization,
invoked by the "minimize"_minimize.html command.

IMPORTANT NOTE: If you want the atom/wall interaction energy to be
included in the total potential energy of the system (the quantity
being minimized), you MUST enable the "fix_modify"_fix_modify.html
{energy} option for this fix.

[Restrictions:]

Any dimension (xyz) that has a LJ 9/3 wall must be non-periodic.

[Related commands:]

"fix wall/reflect"_fix_wall_reflect.html, "fix
wall/lj126"_fix_wall_lj126.html

[Default:] none