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### compute displace/atom command

Syntax:

    compute ID group-ID displace/atom fix-ID

- ID, group-ID are documented in compute command
- displace/atom = style name of this compute command
- fix-ID = ID of a fix of style coord/original

Examples:

    compute 1 all displace/atom myCoords

Description:

Define a computation that calculates the current displacement of each atom in the group from its original coordinates, including all effects due to atoms passing thru periodic boundaries. The original coordinates are stored by a fix coord/original command, whose ID must be specified with this compute. They are the coordinates at the time the fix command was issued. The displacement can be output directly via the dump custom command. It could also be used to calculate a diffusion coefficient for a group of atoms, as is done by the fix msd command.

The value of the displacement will be 0.0 for atoms not in the specified compute group. Note that the fix defines its own group and stores (0.0,0.0,0.0) for the original coordinates of any atom not in the fix group.

Output info:

This compute calculates a vector of length 4 for each atom, which can be accessed by indices 1-4 by any command that uses per-atom computes as input. See this section for an overview of LAMMPS output options. The first 3 components of the vector are the x,y,z displacements. The 4th component is the total displacement, i.e. sqrt(dx*dx + dy*dy + dz*dz).

Restrictions: none

Related commands:

dump custom, fix msd

Default: none