Paratec offers the possibility to fix atoms to their input coordinates, meaning they will not move during the relaxation process. This is simply done by zeroing out the Hellman-Feynman forces. To fix atoms to their original positions, use the stay_put structure. The following example fixes the positions of atoms number 1, 3, and 10.
begin stay_put stay_put 1 stay_put 3 stay_put 10
Default: all atoms are relaxed.