Calculate the centre of mass (CoM) for all structures.
model: The optional structural model number to restrict the calculation of the centre of mass to.
atom_id: The atom identification string to restrict the CoM calculation to.
This user function will calculate the centre of mass (CoM) for all loaded structures, printing out the position and storing it in the current data pipe.
To determine the centre of mass of all structure, simply type:
[numbers=none] relax> structure.com()