| & | Concatenate the next line onto the end of the current line |
| 1SCF | Use the MOPAC keyword 1SCF |
| ALL | In parameter optimization, include reference data that are NOT to be optimized |
| AM1 | Use AM1 parameters |
| CHKPAR | Check parameter Hessian only |
| CLEAN | Remove diagnostic keywords from data set |
| CYCLES=n | Run 'n' cycles of parameter optimization, then stop |
| DEP | Output a file named "parameters_for_PM8_C.F90" |
| DERIV | Print derivatives used by PARAM (d(ref. fn.)/d(parameter) |
| EXPORT | Remove reference data from new data set |
| EXTERNAL=m | External parameter set locations |
| FULL | Print weighted derivatives used by PARAM (d(ref. fn.)/d(parameter)*error |
| GNORM=n | In PARAM, the criterion for geometry optimization is GNORM=N |
| LARGE | Generate MOPAC-type output (for debugging) |
| LBFGS | Use the LBFGS optimizer instead of the EF optimizer in geometry optimizations |
| LET | Let job continue even if some data are missing |
| MAXATOMS=n | Only use systems with 'n' or fewer atoms (abb.: MAXAT=n) |
| MNDO | Use MNDO parameters |
| MNDOd | Use MNDOd parameters |
| NEW_REF=m | Save optimized geometries in directory 'm' |
| NOLIM | Remove limit constraints on parameter values |
| NOSAVEP | Do not save parameters at the end of each cycle of parameter optimization |
| NOSCALE | Do not alter weights even when predicted and calculated errors are different. |
| NUMOPT=n | Restrict parameter optimization to the n worst parameters |
| ONLY | Use only compounds that contain elements being parameterized. |
| OUT=m | Write output file into directory 'm' |
| PARAB=n | Dampening factor for parameter optimization = 'n' |
| PM3 | Use PM3 parameters |
| PM6xxx | Use PM6 parameters |
| PM7xxx | Use PM7 parameters |
| PM8 | Use PM8 parameters |
| POWER=n.nn | Error function minimized is sum((calc-exp)**n.nn), default: 2.0 |
| PRECISE | Use the MOPAC keyword PRECISE. |
| REF=m | Reference data to be read from directory 'm' |
| RELD=n.nn | Default weights for Dipole Moments to be multiplied by n.nn |
| RELG=n.nn | Default weights for Geometries to be multiplied by n.nn |
| RELH=n.nn | Default weights for Heats of Formation to be multiplied by n.nn |
| RELI=n.nn | Default weights for I.P.s to be multiplied by n.nn |
| SET=text | The set of MOPAC reference data files is in file text |
| SURVEY | Generate publication-quality tables in HTML format. |