Syntax:
compute ID group-ID ke/atom
Examples:
compute 1 all ke/atom
Description:
Define a computation that calculates the centro-symmetry parameter for each atom in a group. This can be output via the dump custom command.
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. In solid state systems this 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 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.
Restrictions: none
Related commands: none
Default: none
(Kelchner) Kelchner, Plimpton, Hamilton, Phys Rev B, 58, 11085 (1998).