COM

Calculate the center of mass for a group of atoms.

The computed center of mass is stored as a virtual atom that can be accessed in an atom list through the label for the COM action that creates it.

For arbitrary weights (e.g. geometric center) see CENTER.

The atoms involved can be specified using

ATOMS

the list of atoms which are involved the virtual atom's definition

Examples

The following input instructs plumed to print the distance between the center of mass for atoms 1,2,3,4,5,6,7 and that for atoms 15,20:

COM ATOMS=1-7         LABEL=c1
COM ATOMS=15,20       LABEL=c2
DISTANCE ATOMS=c1,c2  LABEL=d1
PRINT ARG=d1

(See also DISTANCE and PRINT).