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fix_coord_original.html
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Tue, Dec 24, 17:43
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rLAMMPS lammps
fix_coord_original.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 coord/original command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
fix ID group-ID coord/original
</PRE>
<UL><LI>
ID, group-ID are documented in
<A
HREF =
"fix.html"
>
fix
</A>
command
<LI>
coord/original = style name of this fix command
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
fix 1 all coord/original
</PRE>
<P><B>
Description:
</B>
</P>
<P>
Store the original coordinates of atoms in the group at the time the
fix command is issued. This is useful for computing a displacement of
the atoms at later times, via the
<A
HREF =
"compute_displace_atom.html"
>
compute
displace/atom
</A>
command. Or the original
coordinates can be accessed by other
<A
HREF =
"Section_howto.html#4_15"
>
output
commands
</A>
that use per-atom quantities such as
the
<A
HREF =
"dump.html"
>
dump custom
</A>
command.
</P>
<P>
IMPORTANT NOTE: The original coordinates are stored in "unwrapped"
form, by using the image flags associated with each atom. See the
<A
HREF =
"dump.html"
>
dump custom
</A>
command for a discussion of "unwrapped"
coordinates. See the Atoms section of the
<A
HREF =
"read_data.html"
>
read_data
</A>
command for a discussion of image flags and how they are set for each
atom. You can reset the image flags (e.g. to 0) before invoking this
fix by using the
<A
HREF =
"set.html"
>
set image
</A>
command.
</P>
<P>
IMPORTANT NOTE: If an atom is part of a rigid body (see the
<A
HREF =
"fix_rigid.html"
>
fix
rigid
</A>
command), it's periodic image flags are altered,
and its original coordinates may not be what you expect. See the
<A
HREF =
"fix_rigid.html"
>
fix rigid
</A>
command for details.
</P>
<P><B>
Restart, fix_modify, output, run start/stop, minimize info:
</B>
</P>
<P>
This fix writes the original coordinates of the atoms to
<A
HREF =
"restart.html"
>
binary
restart files
</A>
, so that the values can be restored when a
simulation is restarted. See the
<A
HREF =
"read_restart.html"
>
read_restart
</A>
command for info on how to re-specify a fix in an input script that
reads a restart file, so that the operation of the fix continues in an
uninterrupted fashion.
</P>
<P>
None of the
<A
HREF =
"fix_modify.html"
>
fix_modify
</A>
options are relevant to this
fix.
</P>
<P>
This fix produces a per-atom vector which can be accessed by various
<A
HREF =
"Section_howto.html#4_15"
>
output commands
</A>
. The length of the vector
for each atom is 3, and the components store the original unwrapped
x,y,z coords of each atom. The per-atom values be accessed on any
timestep.
</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. This fix is not invoked during
<A
HREF =
"minimize.html"
>
energy
minimization
</A>
.
</P>
<P><B>
Restrictions:
</B>
none
</P>
<P><B>
Related commands:
</B>
</P>
<P><A
HREF =
"fix_msd.html"
>
fix msd
</A>
</P>
<P><B>
Default:
</B>
none
</P>
</HTML>
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