CENTER_FAST
This is part of the vatom module

Calculate the center for a group of atoms, with arbitrary weights.

Examples
Glossary of keywords and components
Description of components

By default this Action calculates the following quantities. These quantities can be referenced elsewhere in the input by using this Action's label followed by a dot and the name of the quantity required from the list below.

Quantity Description
x the x coordinate of the virtual atom
y the y coordinate of the virtual atom
z the z coordinate of the virtual atom
mass the mass of the virtual atom
charge the charge of the virtual atom
The atoms involved can be specified using
ATOMS the list of atoms which are involved the virtual atom's definition. For more information on how to specify lists of atoms see Groups and Virtual Atoms
Options
NOPBC ( default=off ) ignore the periodic boundary conditions when calculating distances
MASS ( default=off ) If set center is mass weighted
PHASES

( default=off ) Compute center using trigonometric phases

WEIGHTS Center is computed as a weighted average.
SET_CHARGE Set the charge of the virtual atom to a given value.
SET_MASS Set the mass of the virtual atom to a given value.