# Input keywords¶

This manual documents the input for the MOPAC engine used together with the AMS driver. If you are not yet familiar with the AMS driver setup, we highly recommend reading the introductory section in the AMS manual.

The MOPAC engine is selected and configured in the AMS input with

Engine MOPAC
... keywords documented in this manual ...
EndEngine


This page documents all keywords of the MOPAC engine input, basically the contents of the Engine MOPAC block in the AMS input file.

General remarks on the input syntax can be found in the AMS manual.

The Examples section of this manual contains several example calculations

## Model Hamiltonian¶

The most important keyword in the MOPAC engine input is the model selection:

Model
Type: Multiple Choice PM7 [AM1, MNDO, MNDOD, PM3, RM1, PM6, PM6-D3, PM6-DH+, PM6-DH2, PM6-DH2X, PM6-D3H4X, PM7] Method Selects the model Hamiltonian to use in the calculation. AM1: Use the AM1 Hamiltonian. MNDO: Use the MNDO Hamiltonian. MNDOD: Use the MNDO-d Hamiltonian. RM1: Use the RM1 Hamiltonian. PM3: Use the MNDO-PM3 Hamiltonian. PM6: Use the PM6 Hamiltonian. PM6-D3: Use the PM6 Hamiltonian with Grimme’s D3 corrections for dispersion. PM6-DH+: Use the PM6 Hamiltonian with corrections for dispersion and hydrogen-bonding. PM6-DH2: Use the PM6 Hamiltonian with corrections for dispersion and hydrogen-bonding. PM6-DH2X: Use PM6 with corrections for dispersion and hydrogen and halogen bonding. PM6-D3H4: Use PM6 with Rezac and Hobza’s D3H4 correction. PM6-D3H4X: Use PM6 with Brahmkshatriya, et al.’s D3H4X correction. PM7: Use the PM7 Hamiltonian. PM7-TS: Use the PM7-TS Hamiltonian (only for barrier heights)

The default PM7 model [2] is the latest parametrization for MOPAC and should be the most accurate for most calculations.

EField
Type: Float List Hartree/(e Bohr) Apply the specified homogeneous external electric field. You must specify 3 numbers corresponding to the the x,y and z component of the electric field. Note: EFiled should only be used for single point calculations.
Sparkles
Type: Bool False Represent lanthanides by their fully ionized 3+ sparkles. That is, they have no basis set, and therefore cannot have a charge different from +3. When using sparkles, the geometries of the lanthanides are reproduced with good accuracy, but the heats of formation and electronic properties are not accurate.
UnpairedElectrons
Type: Integer Spin polarization If this key is present, a spin-unrestricted calculation with the specified number of unpaired electrons is performed. If this key is not present the number of unpaired electrons is determined automatically (0 for systems with an even number of electrons, 1 for radicals), and a restricted or unrestricted calculation is performed accordingly.

## Solvation¶

Solvation effects can be included via the COSMO model.

Solvation
Enabled [True | False]
NSPA [...]
Solvent
Eps float
Name [...]
End
End

Solvation
Type: Block Options for the COSMO (Conductor like Screening Model) solvation model.
Enabled
Type: Bool False Use COSMO Use the Conductor like Screening Model (COSMO) to include solvent effects.
NSPA
Type: Multiple Choice 42 [12, 32, 42, 92, 122, 162, 252, 272, 362, 482, 492, 642, 752] NSPA Maximum number of COSMO surface points per atom.
Solvent
Type: Block Solvent details
Eps
Type: Float Dielectric constant User-defined dielectric constant of the solvent (overrides the Eps value of the solvent defined in ‘Name’)
Name
Type: Multiple Choice Water [CRS, AceticAcid, Acetone, Acetonitrile, Ammonia, Aniline, Benzene, BenzylAlcohol, Bromoform, Butanol, isoButanol, tertButanol, CarbonDisulfide, CarbonTetrachloride, Chloroform, Cyclohexane, Cyclohexanone, Dichlorobenzene, DiethylEther, Dioxane, DMFA, DMSO, Ethanol, EthylAcetate, Dichloroethane, EthyleneGlycol, Formamide, FormicAcid, Glycerol, HexamethylPhosphoramide, Hexane, Hydrazine, Methanol, MethylEthylKetone, Dichloromethane, Methylformamide, Methypyrrolidinone, Nitrobenzene, Nitrogen, Nitromethane, PhosphorylChloride, IsoPropanol, Pyridine, Sulfolane, Tetrahydrofuran, Toluene, Triethylamine, TrifluoroaceticAcid, Water] Solvent Name of a pre-defined solvent. A solvent is characterized by the dielectric constant (Eps) and the solvent radius (Rad).
Rad
Type: Float Angstrom Radius User-defined radius of the solvent molecule (overrides the Rad value of the solvent defined in ‘Name’).

## Properties¶

Properties
StaticPolarizability [True | False]
pKa [True | False]
End

Properties
Type: Block MOPAC can calculate various properties of the simulated system. This block configures which properties will be calculated.
StaticPolarizability
Type: Bool False Calculate the static polarizability. An electric field gradient is applied to the system, and the response is calculated. The dipole and polarizability are calculated two different ways, from the change in heat of formation and from the change in dipole. A measure of the imprecision of the calculation can be obtained by comparing the two quantities.
pKa
Type: Bool False pKa If requested, the pKa of hydrogen atoms attached to oxygen atoms is calculated and printed.

The calculation of Natural Bond Orbitals can be requested with the following keyword:

CalcLocalOrbitals [True | False]

CalcLocalOrbitals
Type: Bool False Compute and print the localized orbitals, also known as Natural Bond Orbitals (NBO). This is equivalent to the LOCAL mopac keyword.

The calculation of bond orders can be requested in the AMS Properties block.

## Technical settings¶

SCF
CampKingConverger [True | False]
ConvergenceThreshold float
MaxIterations integer
End

SCF
Type: Block Options for the self-consistent field procedure.
CampKingConverger
Type: Bool False Use Camp-King Use the Camp-King SCF converger. This is a very powerful, but CPU intensive, SCF converger.
ConvergenceThreshold
Type: Float 0.0001 kcal/mol If the difference in energy between two successive SCF iterations is smaller than this value, the SCF procedure is considered converged.
MaxIterations
Type: Integer 2000 Maximum number of SCF iterations.

With the MOZYME method the standard SCF procedure is replaced with a localized molecular orbital (LMO) method. This can speed-up the calculation of large molecules. Although a job that uses the MOZYME technique should give results that are the same as conventional SCF calculations, in practice there are differences. Most of these differences are small, but in some jobs the differences between MOZYME and conventional SCF calculations can be significant. Use with care.

Mozyme
Type: Bool False Replace the standard SCF procedure with a localized molecular orbital (LMO) method. The time required for an SCF cycle when Mozyme is used scales linearly with system size.

## Extra keywords¶

Finally it is possible to pass any other keywords directly to the MOPAC program [1]. The full list of keywords can be found on the standalone MOPAC manual.

Keywords string

Keywords
Type: String A string containing all the desired custom MOPAC keywords. Basically for anything not directly supported through AMS.

These keywords are just literally passed through to MOPAC program which the AMS MOPAC engine wraps, without any checking in AMS. One should therefore be very careful with this, as it is very easy to set up completely non-sensical calculations in this way.

Note: The following keywords have been either removed or renamed in our version of MOPAC and they should not be used in the Keywords key: 0SCF, 1SCF, A0, ADD, AIDER, AIGIN, AIGOUT, ALT_A, ALT_R, ANGSTROMS, AUTOSYM, BANANA, BAR, BCC, BFGS, BIGCYCLES, BIRADICAL, CHAINS, COMPARE, CVB, DDMAX, DDMIN, DFORCE, DFP, DMAX, DRC, ECHO, EF, FLEPO, FORCE, FREQCY, GNORM, H, HTML, INT, IONIZE, IRC, ISOTOPE, KINETIC, LBFGS, LET, LOCATE, MODE, NOCOMMENTS, NOOPT, NORESEQ, NOSWAP, NOTER, NOTHIEL, NOTXT, OPT, P, PDB, PDBOUT, POINT, POINT1, POINT2, RABBIT, RECALC, RMAX, RMIN, SIGMA, SLOG, SMOOTH, SNAP, START_RES, STEP, STEP1, STEP2, SYBYL, T, THERMO, THREADS, TIMES, TRANS, TS, VELOCITY, X, XENO, XYZ,, AM1, LOCAL, BONDS, CHARGE, UHF, CAMP, KING, ITRY, EPS, FIELD, pKa, STATIC, CYCLES, PRESSURE, SPARKLE.