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.

Model Hamiltonian¶

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

Model

Type: Multiple Choice
Default value: PM7
Options: [AM1, MNDO, MNDOD, PM3, RM1, PM6, PM6-D3, PM6-DH+, PM6-DH2, PM6-DH2X, PM6-D3H4X, PM7]
GUI name: Method
Description: 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.

Sparkles

Type: Bool
Default value: No
Description: 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
GUI name: Spin polarization
Description: 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 Yes/No
   NSPA [...]
   Solvent
      Eps float
      Name [...]
      Rad float
   End
End

Solvation

Type: Block
Description: Options for the COSMO (Conductor like Screening Model) solvation model.

Enabled

Type: Bool
Default value: No
GUI name: Use COSMO
Description: Use the Conductor like Screening Model (COSMO) to include solvent effects.

NSPA

Type: Multiple Choice
Default value: 42
Options: [12, 32, 42, 92, 122, 162, 252, 272, 362, 482, 492, 642, 752]
GUI name: NSPA
Description: Maximum number of COSMO surface points per atom.

Solvent

Type: Block
Description: Solvent details

Eps

Type: Float
GUI name: Dielectric constant
Description: User-defined dielectric constant of the solvent (overrides the Eps value of the solvent defined in ‘Name’)

Name

Type: Multiple Choice
Default value: Water
Options: [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]
GUI name: Solvent
Description: Name of a pre-defined solvent. A solvent is characterized by the dielectric constant (Eps) and the solvent radius (Rad).

Rad

Type: Float
Unit: Angstrom
GUI name: Radius
Description: User-defined radius of the solvent molecule (overrides the Rad value of the solvent defined in ‘Name’).

Properties¶

Properties
   StaticPolarizability Yes/No
   pKa Yes/No
End

Properties

Type: Block
Description: MOPAC can calculate various properties of the simulated system. This block configures which properties will be calculated.

StaticPolarizability

Type: Bool
Default value: No
Description: 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
Default value: No
GUI name: pKa
Description: 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 Yes/No

CalcLocalOrbitals

Type: Bool
Default value: No
Description: 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 Yes/No
   ConvergenceThreshold float
   MaxIterations integer
End

SCF

Type: Block
Description: Options for the self-consistent field procedure.

CampKingConverger

Type: Bool
Default value: No
GUI name: Use Camp-King
Description: Use the Camp-King SCF converger. This is a very powerful, but CPU intensive, SCF converger.

ConvergenceThreshold

Type: Float
Default value: 0.0001
Unit: kcal/mol
Description: If the difference in energy between two successive SCF iterations is smaller than this value, the SCF procedure is considered converged.

MaxIterations

Type: Integer
Default value: 2000
Description: 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
Default value: No
Description: 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
Description: 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.