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fix_wall_lj126.html
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Sun, Nov 3, 23:50
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rLAMMPS lammps
fix_wall_lj126.html
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<HTML>
<CENTER><A
HREF =
"http://lammps.sandia.gov"
>
LAMMPS WWW Site
</A>
-
<A
HREF =
"Manual.html"
>
LAMMPS Documentation
</A>
-
<A
HREF =
"Section_commands.html#comm"
>
LAMMPS Commands
</A>
</CENTER>
<HR>
<H3>
fix wall/lj126 command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
fix ID group-ID wall/lj126 style coord epsilon sigma cutoff
</PRE>
<UL><LI>
ID, group-ID are documented in
<A
HREF =
"fix.html"
>
fix
</A>
command
<LI>
wall/lj126 = style name of this fix command
<LI>
style =
<I>
xlo
</I>
or
<I>
xhi
</I>
or
<I>
ylo
</I>
or
<I>
yhi
</I>
or
<I>
zlo
</I>
or
<I>
zhi
</I>
<LI>
coord = position of wall
<LI>
epsilon = Lennard-Jones epsilon for wall-particle interaction
<LI>
sigma = Lennard-Jones sigma for wall-particle interaction
<LI>
cutoff = distance from wall at which wall-particle interaction is cut off
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
fix wallhi all wall/lj126 xhi 10.0 1.0 1.0 1.12
</PRE>
<P><B>
Description:
</B>
</P>
<P>
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 12-6 potential
</P>
<CENTER><IMG
SRC =
"Eqs/pair_lj.jpg"
>
</CENTER>
<P>
where
<I>
r
</I>
is the distance from the particle to the wall
<I>
coord
</I>
, and
epsilon and sigma are the usual LJ parameters. Rc is the cutoff value
specified in the command. This interaction provides a harder, more
repulsive interaction with the wall than the softer 9-3 potential
provided by the
<A
HREF =
"fix_wall_lj93.html"
>
fix wall/lj93
</A>
command.
</P>
<P>
The wall potential is shifted so that the energy of a wall-particle
interaction is 0.0 at the cutoff distance.
</P>
<P><B>
Restart, fix_modify, thermo output, run start/stop, minimize info:
</B>
</P>
<P>
No information about this fix is written to
<A
HREF =
"restart.html"
>
binary restart
files
</A>
.
</P>
<P>
The
<A
HREF =
"fix_modify.html"
>
fix_modify
</A>
<I>
energy
</I>
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
<A
HREF =
"thermo_style.html"
>
thermodynamic
output
</A>
.
</P>
<P>
This fix computes a scalar energy and a 3-vector of forces (on the
wall), which can be accessed by various
<A
HREF =
"Section_howto.html#4_15"
>
output
commands
</A>
.
</P>
<P>
No parameter of this fix can be used with the
<I>
start/stop
</I>
keywords of
the
<A
HREF =
"run.html"
>
run
</A>
command.
</P>
<P>
The forces due to this fix are imposed during an energy minimization,
invoked by the
<A
HREF =
"minimize.html"
>
minimize
</A>
command.
</P>
<P>
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
<A
HREF =
"fix_modify.html"
>
fix_modify
</A>
<I>
energy
</I>
option for this fix.
</P>
<P><B>
Restrictions:
</B>
</P>
<P>
Any dimension (xyz) that has a LJ 12/6 wall must be non-periodic.
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"fix_wall_reflect.html"
>
fix wall/reflect
</A>
,
<A
HREF =
"fix_wall_lj93.html"
>
fix
wall/lj93
</A>
</P>
<P><B>
Default:
</B>
none
</P>
</HTML>
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