Note
This website is presently under development. The primary website for MOPAC is still http://openmopac.net until the majority of its contents have been migrated here.
Keywords¶
By default, MOPAC input files contain one line of keywords followed by two lines of comments. MOPAC’s keywords are strings that can include letters, numbers, and special characters. Keywords are separated by whitespace, and their order is irrelevant. While the MOPAC documentation, output files, and source code treat all keyword letters as being uppercase, the specification of keywords in the input file is not case sensitive.
Keywords either appear by themselves or with the specification of additional values that can be integers, real numbers, or strings.
In some cases, one or more of these additional values is optional.
The syntax for specifying these values is keyword-specific and not fully standardized.
For one value, the syntax is either KEYWORD=value, KEYWORD(value), or KEYWORD-value.
For multiple values, the syntax is either KEYWORD=(value1,value2,...,valueN) or KEYWORD(value1,value2,...,valueN).
In all cases, whitespace is not allowed in a keyword statement outside string values with delimiters.
MOPAC can parse real numbers in scientific notation with d, D, e, or E separating the mantissa and exponent.
String values do not include a delimiter unless explicitly stated in the keyword syntax, either "string" or (string).
Older versions of MOPAC contain keywords that are no longer officially supported. While MOPAC continues to support obsolete keywords to maintain backward compatibility, they are not recommended or documented on this website.
Each keyword has its own webpage that describes its usage and syntax and specifies the number, type, and purpose of its additional values.
Glossary
Extend the line of keywords to the next line of the input file |
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Read input file, then stop before the SCF cycle |
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Print the matrix of one-electron resonance integrals |
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Converge one SCF cycle, then stop before geometry relaxation |
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Read the input geometry in atomic units (bohr) |
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Add hydrogen atoms to close the valence shell of an organic molecule |
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Read the input geometry in Gaussian Z-matrix format |
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Write the output geometry in Gaussian Z-matrix format to the |
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Print the final bond-order matrix, including weak bonds and H atoms (MOZYME only) |
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Print all MO eigenvectors |
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In PDB files with alternative atoms, select atoms A |
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Use the AM1 model |
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Read the input geometry in angstroms |
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Automatically impose a subset of SYMMETRY constraints |
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Output auxiliary information for use by other programs |
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Generate localized molecular orbitals with hybrid orbitals for double bonds |
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reduce bar length by a maximum of n.nn% |
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Only even unit cells used (used by BZ) |
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Use the Flepo or BFGS geometry optimizer |
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Do a maximum of n big steps |
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Target a biradical ground state |
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Print the final bond-order matrix |
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Output data for Program BZ - analysis of the Brillouin Zones |
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Define an active space for CI calculations (INDO compatible) |
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Define an active space for double excitations (INDO only) |
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Use Camp-King converger in SCF |
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Print point-group character table |
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In a protein, explicitely define the letters of chains. |
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Total electric charge on the system (MOZYME compatible) |
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Print net charge on system, and all charges in the system |
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Print details of working in CHARST |
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Report possible faults in input geometry |
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Restrict an active space to 1-electron excitations |
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Restrict an active space to 1 & 2-electron excitations (INDO compatible) |
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Restrict an active space to 1, 2, & 3-electron excitations |
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Compare the geometries of two systems |
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Print heat of formation calculated in COMPFG |
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Add in COSMO charge corrections |
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Write details of the solvent accessible surface to a file |
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In MOZYME, the interatomic distance where the NDDO approximation stops (default: 10 Ångstroms) |
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Madelung distance cutoff is n.nn Ångstroms. This can speed up the calculations (default: 30 Ångstroms) |
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In MOZYME, the interatomic distance beyond which overlap integrals are ignored (default: 7 Ångstroms) |
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In MOZYME. add and remove specific bonds to allow a Lewis or PDB structure. |
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Do a maximum of n steps |
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n MOZYME. damp SCF oscillations using a factor of n.nn |
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Input data set is re-defined to text |
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Print part of working in DCART |
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See EF code |
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Minimum trust radius in a EF/TS calculation |
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Debug option turned on |
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Print working in PULAY |
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Density matrix output |
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Formatted density matrix output |
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Print final density matrix |
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Print part of working in DERI1 |
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Print part of working in DERI2 |
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Print part of working in DERIT |
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Print part of working in DERIV |
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Print part of working in DERNVO |
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Force calculation specified, also print force matrix. |
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Use Davidson-Fletcher-Powell method to optimize geometries |
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In animations graphs, replace ΔHf with dipole |
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Distance for interactions in fine grid in COSMO |
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Print post-SCF corrections to the heat of formation |
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Maximum stepsize in eigenvector following |
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Target a doublet spin state |
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Dynamic reaction coordinate calculation |
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Write restart files every n seconds |
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Data are echoed back before calculation starts |
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Use the EigenFollowing routine for geometry optimization |
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Print canonical eigenvectors instead of LMOs in MOZYME calculations |
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Print all eigenvalues in ITER |
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Partition energy into components |
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Dielectric constant in COSMO calculation |
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Do not use. Use GRAPHF instead. |
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Do not use. Use GRAPHF instead. |
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Calculate RHF spin density |
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Target the first excited singlet state |
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Read parameters off disk |
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An external electric field is to be used |
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In RHF open and closed shell, force M.O. n to be filled |
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Print details of geometry optimization |
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Print details of working in FMAT |
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Print last Fock matrix |
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Calculate vibrational frequencies |
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Calculate vibrational frequencies for a transition state |
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Print symmetrized Hessian in a FORCE calculation |
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Override some safety checks |
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Read in geometry from the file <text> |
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Read in a second geometry from the file <text> |
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Exit when gradient norm drops below n .n kcal/mol/Angstrom |
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Print all gradients |
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Generate unformatted file for graphics |
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Generate formatted file for graphics suitable for Jmol and MOPETE. |
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Heat of formation takes priority in DRC |
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Print all parameters used, the one-electron matrix, and two-electron integrals |
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Options for calculating Hessian matrices in EF |
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Print Hessian from geometry optimization |
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Write a web-page for displaying and editing a protein |
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Hyperfine coupling constants to be calculated |
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Use the INDO/S model for excited states |
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Make all coordinates internal coordinates |
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Reverse all optimization flags |
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Do not use - use SITE=(IONIZE) instead |
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Intrinsic reaction coordinate calculation |
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Force matrix written to disk (channel 9 ) |
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Print details of working in ITER |
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Set limit of number of SCF iterations to n |
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Mode of Hessian update in eigenvector following |
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Excess kinetic energy added to DRC calculation |
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Use Camp-King converger for SCF |
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Print expanded output |
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Use the low-memory version of the BFGS optimizer |
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Override certain safety checks |
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Print the Lewis structure |
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Print details of line minimization |
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Print localized orbitals. These are also called Natural Bond Orbitals or NBO |
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Given reactants and products, locate the transition state connecting them |
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Generate a log file |
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Maximum number of configurations in the active space (INDO only) |
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Print details of MECI calculations |
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Keyword generated by MAKPOL for use with programBZ |
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Make specified atoms 100% ionic |
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Restrict an active space to a list of microstates |
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Reduce the size of the output by only printing specified atoms |
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Minimize MEP minima in the plane defined |
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Use molecular mechanics correction to CONH bonds |
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Use the MNDO model |
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Use the MNDO-d model |
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In EF, follow Hessian mode no. n |
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Print details of working in MOLDAT |
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Print details of working in MOLSYM |
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Use old MOPAC definition for 2nd and 3rd atoms |
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Use the Localized Molecular Orbital method to speed up the SCF |
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Use an active space of excitations from multiple reference states (INDO only) |
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Target a spin state by its spin quantum number |
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Print the Mulliken population analysis |
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In excited state COSMO calculations, set the value of N**2 |
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Minimize gradients using NLLSQ |
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Use numerical CI derivatives (analytical derivatives are the default) |
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Ignore all lines except ATOM, HETATM, and TER in PDB files |
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Suppress log file trail, where possible |
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Do not use molecular mechanics correction to CONH bonds |
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Target a nonet spin state |
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Do not use Newton-Raphson method in EF |
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Do not optimize the coordinates of all atoms of type X |
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In symmetry work, FORCE calculations, and whenGEO_REF is used, use the supplied orientation |
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Suppress the default re-sequencing of atoms to the PDB sequence |
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Do not allow atom swapping when GEO_REF is used |
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Reduce point-group symmetry to C1 |
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Do not put "TER"s in PDB files |
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Do not use Thiel’s FSTMIN technique |
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Remove any text from atom symbols |
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Do not print Cartesian coordinates |
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Sets number of geometric segments in COSMO |
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Number of surfaces in an ESP calculation |
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Target an octet spin state |
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In COSMO, use the old Solvent Accessible Surface calculation |
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Read initial density matrix off disk |
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Use the old fundamental physical constants |
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Previous geometry to be used |
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In TS, minimum allowed overlap of eigenvectors |
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Distribute electrons over partially occupied orbitals |
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Optimize coordinates of all atoms within n.nn Ångstroms of atoms labeled "text" |
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Optimize the coordinates of all atoms of type X |
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Reduce the amount of output (useful for large systems) |
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An applied pressure of n.nn Newtons/m2 to be used |
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Input geometry is in protein data bank format |
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User defined chemical symbols in protein data base |
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Output geometry in pdb format |
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Restrict an active space to 1-electron and paired 2-electron excitations |
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Resolve density matrix into σ, π, and δ components |
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Print the pKa for ionizable hydrogen atoms attached to oxygen atoms |
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Monitor convergence of density matrix in ITER |
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Use the PM3 model |
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Use the PM6 model |
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Use PM6 with the D3 model for dispersion |
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Use PM6 with the D3H4 model for dispersion and hydrogen bonding |
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Use PM6 with the D3H4X model for dispersion and hydrogen/halogen bonding |
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Use PM6 with the DH+ model for dispersion and hydrogen bonding |
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Use PM6 with the DH2 model for dispersion and hydrogen bonding |
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Use PM6 with the DH2X model for dispersion and hydrogen/halogen bonding |
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Use the PM7 model (default) |
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Use the PM7-TS model for transition states |
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Complete semiempirical MEP calculation |
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Complete semiempirical MEP in a plane to be defined |
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Number of points in reaction path |
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Number of points in first direction in grid calculation |
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Number of points in second direction in grid calculation |
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Calculate first, second and third order polarizabilities |
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In ESP, write out electrostatic potential to unit 21 |
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Print details of working in POWSQ |
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More stringent criteria are used |
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Apply pressure or tension to a solid or polymer |
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Print details of geometry optimization in EF |
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Print charges in ARC file |
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Print interatomic distances |
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MEP contour data output to <filename>.mep |
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Print Cartesian coordinates |
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Use Pulay’s converger to obtain a SCF |
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Incorporate environmental effects in the QM/MM approach |
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Charges derived from Wang-Ford type AM1 MEP |
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Target a quartet spin state |
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Target a quintet spin state |
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Generate localized molecular orbitals with hybrid orbitals for double bonds |
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Print Ramachandra angles for the residues in a protein |
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In MOZYME geometry optimizations, only use atoms being optimized in the SCF |
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During and at end of MOZYME calculation, re-localize the LMOs |
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In EF, recalculate Hessian every n steps |
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Default SCF criterion multiplied by n |
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In MOZYME, re-orthogonalize LMO’s each 10 SCF calculations. |
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Re-arrange the atoms to match the PDB convention |
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Label each atom in a polypeptide with the amino acid residue |
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Calculation restarted |
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Use a restricted Hartree-Fock Hamiltonian |
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Use the RM1 model |
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In TS, maximum allowed ratio for energy change |
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In TS, minimum allowed ratio for energy change |
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Target an excited state by energy or symmetry |
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In EF, scale p-RFO to trust radius |
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Effective radius of solvent in COSMO |
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Optimize transition state |
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Scaling factor for van der waals distance in ESP |
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Default SCF criterion replaced by the value supplied |
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Increment between layers in ESP |
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Target a septet spin state |
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In MOZYME, some π bonds are explicitly set by the user |
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Extra keywords to be read from setup file |
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Target a sextet spin state |
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a damping factor of n defined to start SCF |
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Minimize gradients using SIGMA |
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Target a singlet spin state |
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Define ionization state of residues in proteins |
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In L-BFGS optimization, use fixed step of length n .nn |
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Multiplier used to scale MNDO charges |
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In a GRID calculation, remove artifacts caused by the order in which points are calculated |
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Snap Z-matrix angles to common high-symmetry values |
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Use sparkles instead of atoms with basis sets |
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Print final UHF spin matrix |
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Define starting residue numbers in a protein, if different from the default |
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Calculate Polarizability using electric fields |
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Step size in path |
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Step size n for first coordinate in grid calculation |
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Step size n for second coordinate in grid calculation |
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Deorthogonalize orbitals in STO-3G basis |
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Print superdelocalizabilities |
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Output a file for use by Tripos’s SYBYL program |
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Average symmetry equivalent ESP charges |
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Impose Z-matrix and Cartesian coordinate constraints |
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Print characters of eigenvectors and print number of I.R.s |
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Print details of working in subroutine SYMTRZ. |
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A time of n seconds requested |
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Time takes priority in DRC |
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Output transition-dipole moments between excited states (INDO only) |
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Perform a thermodynamics calculation |
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Print times of various stages |
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The system is a transition state (used in thermodynamics calculation) |
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Target a triplet spin state |
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Using EF routine for TS search |
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Use an unrestricted Hartree-Fock Hamiltonian |
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Van der waals radius for atoms in COSMO defined by user |
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Van der waals radius for atoms in MOZYME defined by user |
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Print final vectors |
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Supply the initial velocity vector in a DRC calculation |
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Use Williams surface |
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Maximum number of excited states to print (INDO only) |
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Coefficient threshold for printing components of an excited state (INDO only) |
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Geometry changes take priority in DRC |
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Allow non-standard residues in proteins to be labeled. |
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Do all geometric operations in Cartesian coordinates |
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Number of mers in a cluster |