Syntax:
compute ID group-ID centro/atom
Examples:
compute 1 all centro/atom
Description:
Define a computation that calculates the centro-symmetry parameter for each atom in a 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 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 (i.e. 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 of a centro/atom style.
Output info:
This compute calculates a scalar quantity for each atom, which can be accessed by any command that uses per-atom computes as input. See this section for an overview of LAMMPS output options.
Restrictions: none
Related commands: none
Default: none
(Kelchner) Kelchner, Plimpton, Hamilton, Phys Rev B, 58, 11085 (1998).