compute com command
compute ID group-ID com
ID, group-ID are documented in compute command
com = style name of this compute command
compute 1 all com
Define a computation that calculates the center-of-mass of the group of atoms, including all effects due to atoms passing through periodic boundaries.
A vector of three quantities is calculated by this compute, which are the x,y,z coordinates of the center of mass.
The coordinates of an atom contribute to the center-of-mass 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.
This compute calculates a global vector of length 3, which can be accessed by indices 1-3 by any command that uses global vector values from a compute as input. See the Howto output doc page for an overview of LAMMPS output options.
The vector values are “intensive”. The vector values will be in distance units.