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.

Model [ ... ]
UnpairedElectrons int
Sparkles [True | False]
Properties
   BondOrders [True | False]
End
Mozyme [True | False]
Solvation [None | COSMO-CRS | COSMO-Water]

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-D4H4, PM6-D3H4X, PM7, PM7-TS]
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.

UnpairedElectrons

Type:	Integer
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.

Sparkles

Type:	Bool
Default value:	False
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.

Properties

BondOrders

Type:	Bool
Default value:	False
Description:	Whether or not bond orders are calculated based on the final molecular orbitals.

Mozyme

Type:	Bool
Default value:	False
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.

Solvation

Type:	Multiple Choice
Default value:	None
Options:	[None, COSMO-CRS, COSMO-Water]
Description:	Configures the solvation model. Select COSMO-Water to specify the COSMO solvation method, COSMO-CRS for use with COSMO-RS.

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. E.g. it obviously does not make sense to let the MOPAC program do a geometry optimization, when the AMS driver is really just trying to get energy and gradients for a single geometry.