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### fix store/coord command

Syntax:

    fix ID group-ID store/coord keyword values ...

- ID, group-ID are documented in fix command
- store/coord = style name of this fix command
- zero or more keyword/value pairs may be appended
- keyword = com

        com value = yes or no

Examples:

    fix 1 all store/coord
    fix 1 upper store/coord com yes

Description:

Store the original coordinates of atoms in the group at the time the fix command is issued. This is used for computing a displacement of the atoms at later times, via the compute displace/atom command. Or the original coordinates can be accessed by other output commands that use per-atom quantities such as the dump custom command.

IMPORTANT NOTE: The original coordinates are stored in "unwrapped" form, by using the image flags associated with each atom. See the dump custom command for a discussion of "unwrapped" coordinates. See the Atoms section of the read_data 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 set image command.

IMPORTANT NOTE: If an atom is part of a rigid body (see the fix rigid command), it's periodic image flags are altered, and its original coordinates may not be what you expect. See the fix rigid command for details.

If the com keyword is set to yes then the position of each atom relative to the center-of-mass of the group of atoms is stored, instead of the absolute position. This option is used by the compute msd command.

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

This fix writes the original coordinates of the atoms to binary restart files, so that the values can be restored when a simulation is restarted. See the read_restart 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.

None of the fix_modify options are relevant to this fix.

This fix produces a per-atom array which can be accessed by various output commands. The number of columns for each atom is 3, and the columns store the original unwrapped x,y,z coords of each atom. The per-atom values be accessed on any timestep.

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:

compute msd, compute displace/atom, compute store/force

Default:

The option default is com = no.