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### compute gyration command

Syntax:

    compute ID group-ID gyration

- ID, group-ID are documented in compute command
- gyration = style name of this compute command

Examples:

    compute 1 molecule gyration

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

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 command for a discussion of "unwrapped" coordinates. See the Atoms section of the read_data 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 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 this section for an overview of LAMMPS output options.

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

Restrictions: none

Related commands:

compute gyration/molecule

Default: none