"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

:line

compute gyration command :h3

[Syntax:]

compute ID group-ID gyration :pre

ID, group-ID are documented in "compute"_compute.html command
gyration = style name of this compute command :ul

[Examples:]

compute 1 molecule gyration :pre

[Description:]

Define a computation that calculates the radius of gyration Rg of the
group of atoms, including all effects due to atoms passing thru
periodic boundaries.

Rg is a measure of the size of the group of atoms, and is computed by
this formula

:c,image(Eqs/compute_gyration.jpg)

where M is the total mass of the group, Rcm is the center-of-mass
position of the group, and the sum is over all atoms in the group.

IMPORTANT NOTE: The coordinates of an atom contribute to Rg in
"unwrapped" form, by using the image flags associated with each atom.
See the "dump custom"_dump.html command for a discussion of
"unwrapped" coordinates.  See the Atoms section of the
"read_data"_read_data.html 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 compute by using the "set
image"_set.html command.

[Output info:]

This compute calculates a global scalar (Rg).  This value can be used
by any command that uses a global scalar value from a compute as
input.  See "Section_howto 15"_Section_howto.html#howto_15 for an
overview of LAMMPS output options.

The scalar value calculated by this compute is "intensive".  The
scalar value will be in distance "units"_units.html.

[Restrictions:] none

[Related commands:]

"compute gyration/molecule"_compute_gyration_molecule.html

[Default:] none