| KEYWORD | Description |
|---|---|
| Hamiltonians | |
| PM3 | Use the PM3 Hamiltonian |
| AM1 | Use the AM1 Hamiltonian |
| MNDO | Use the MNDO Hamiltonian |
| MNDO/3 | Use the MNDO/3 Hamiltonian |
| CHARGE=## | Total molecular charge |
| MMOK | If system contains a peptide linkage, add 14 kcal/mol rotation energy barrier as an additional correction |
| NOMM | Do not add the 14 kcal/mol rotation energy barrier to the peptide linkage |
| Routines | |
| NLLSQ | Non Linear Lease Squares routine. More prone to finding a local minimum or transition state "hilltop" than EF, but less likely to diverge |
| EF | Eigenvector Following Routine---faster than NLLSQ, but can fail if far from minimum |
| DMAX | Maximum step size for EF routine |
| HESS=1 | Pre-calulates the Hessian matrix in the EF routine, which saves time |
| RECALC=# | Recalculates the Hessian matriz for the EF routine every # steps. RECALC=10 and DMAX=0.1 can be useful for difficult cases. RECALC=1 and DMAX=0.05 will always find a stationary point if it exists. |
| GNORM=## | Geometry optimization termination criterion. Normally GNORM=0.01 is easily good enough for all high-precision work. |
| PRECISE | Increase criteria for terminating optimizations by 100-fold |
| DFP | Specify the Davidson-Fletcher-Powell method (the Broyden-Fletcher-Goldfarb-Shanno method is the default). |
| Transition State Calculations | |
| SADDLE | Transition State Calculation. See Transition State Example |
| XYZ | Run SADDLE in cartesian coordinates (recommended) |
| BAR=## | Maximum rate of change per step along a transsition state coordinate |
| Thermodynamic Calculations | |
| FORCE | Calculate force constants, which are then used to calculate vibrational frequencies via THERMO |
| THERMO | Thermodynamic quantities are calculated |
| Electro-Static Surface Calculations | |
| ESP | Electro-Static Potential Energy Surface by Merz & Besler |
| NSURF=# | Specifies the number of surface layers in ESP calculation |
| POTWRT | Write surface points and electrostatic potential values to UNIT 21 |
| SCALE | Scaling factor for Van der Waals radii for 1st layer of Connolly surface in ESP |
| SCINCR=#.## | increment between surface layers of ESP calculation |
| SLOPE=#.## | Scale factor for MNDO charges in ESP calculation |
| WILLIAMS | Substitute a Williams surface for the Connolly surface in ESP |
| Output | |
| DIPOLE | Reproduce the cartesial dipole moments |
| NOINTER | Don't print interatomic distances. Reduces output file considerably |
| POLAR | calculate polarizabilities |
| Misc. | |
| T=## | Maximum calculation time in seconds |
| 0SCF | Read in and produce output, but don't do calculation. Useful for validating input data |
| & | Substitutes the next description line for another line of keywords |
| + | The next line is added as a keyword line without deleting a description line |