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### compute centro/atom command

Syntax:

    compute ID group-ID centro/atom

- ID, group-ID are documented in compute command
- centro/atom = style name of this compute command

Examples:

    compute 1 all centro/atom

Description:

Define a computation that calculates the centro-symmetry parameter for each atom in the group. In solid-state systems the centro-symmetry parameter is a useful measure of the local lattice disorder around an atom and can be used to characterize whether the atom is part of a perfect lattice, a local defect (e.g. a dislocation or stacking fault), or at a surface.

The value of the centro-symmetry parameter will be 0.0 for atoms not in the specified compute group.

This parameter is computed using the following formula from (Kelchner)

where the 12 nearest neighbors are found (for fcc lattices) and Ri and Ri+6 are the vectors from the central atom to the opposite pair of nearest neighbors. Atoms not in the group are included in the 12 neighbors used in this calculation.

The neighbor list needed to compute this quantity is constructed each time the calculation is performed (e.g. each time a snapshot of atoms is dumped). Thus it can be inefficient to compute/dump this quantity too frequently or to have multiple compute/dump commands, each with a centro/atom style.

Output info:

This compute calculates a per-atom vector, which can be accessed by any command that uses per-atom values from a compute as input. See this section for an overview of LAMMPS output options.

Restrictions: none

Related commands:

compute cna/atom

Default: none

(Kelchner) Kelchner, Plimpton, Hamilton, Phys Rev B, 58, 11085 (1998).