forked from lijiext/lammps
82 lines
2.7 KiB
Plaintext
82 lines
2.7 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
|
|
|
|
:link(lws,http://lammps.sandia.gov)
|
|
:link(ld,Manual.html)
|
|
:link(lc,Section_commands.html#comm)
|
|
|
|
:line
|
|
|
|
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. The scalar and vector values
|
|
calculated by this fix are "extensive", meaning they scale with the
|
|
number of atoms in the simulation.
|
|
|
|
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
|