Note

This website is presently under development. The primary website for MOPAC is still http://openmopac.net until the majority of its contents have been migrated here.

NOMM

All of the semiempirical methods (MNDO, AM1, PM3, PM6, RM1, PM7) underestimate the barrier to rotation of a peptide bond. A Molecular Mechanics correction has been added which increases the barrier in N-methyl acetamide to 14 kcal/mol. If you do not want this correction, specify NOMM (NO Molecular Mechanics).