2 GRP

This line tells NRLMOL what symmetry to apply to the system. There are some built in symmetries or you may specify your own. The built in symmetries are

• I the identity. No symmetry whatsoever. e.g bromochlorofluoromethane (CHClBrF)
• X and Y linear symmetry. For molecules that form a linear chain. e.g. I$_3$, IBr$_2$
• XY the combination of X and Y symmetry. For molecules with a square shape. e.g. cyclobutane
• TD tetrahedral symmetry. For molecules that form a pyramid structure. e.g. methane
• OD octahedral symmetry. For molecules that form octahedral structures. e.g. PF$_6$
• IH icosahedral symmetry. For molecules with icosahedral structure. e.g., C$_{60}$
• C3V 6-fold rotational symmetry. For molecules with symmetry like that of benzene
• D3D
• D3H

To specify your own symmetry use GRP, and you must write out your own GRPMAT file GRPMAT