MOPAC (Molecular Orbital PACkage) is a semiempirical quantum chemistry program for studying molecules, solids and chemical reactions. It uses simplified quantum-mechanical models whose parameters are fitted to experimental or high-level theoretical data, trading some predictive accuracy for substantially lower computational cost.
The program is primarily command-line driven and uses text input and output files, making it straightforward to incorporate into scripted computational workflows. Its semiempirical approach is particularly useful when conventional ab initio calculations would be too expensive, including screening larger collections of structures and preparing systems for more demanding calculations.
This is free and open source software.
Key Features
- Supports semiempirical Hamiltonians including MNDO, AM1, PM3, RM1, PM6 and PM7.
- Performs molecular and solid-state electronic-structure calculations.
- Optimises molecular geometries and can locate transition states and follow reaction paths.
- Calculates heats of formation, molecular orbitals, gradients and force constants.
- Provides vibrational frequency calculations and thermodynamic analysis.
- Supports closed-shell and open-shell calculations, radicals, ions and polymers.
- Includes COSMO implicit-solvent calculations.
- Calculates polarizabilities and hyperpolarizabilities.
- Accepts Cartesian coordinates, internal coordinates, mixed coordinates and several chemistry-oriented geometry formats.
- Can apply geometry constraints and freeze selected coordinates during optimisation.
- Provides molecular dynamics capabilities for following the time evolution of a system.
- Offers an application programming interface for integrating selected functionality into other software.
- Provides QM/MM facilities for combining quantum-mechanical calculations with an external molecular-mechanics environment.
- Can generate electrostatic-potential and graphics-oriented output for use with molecular visualisation and analysis tools.
- Cross-platform support – runs on Linux, macOS, and Windows.
Website: github.com/openmopac/mopac
Support:
Developer: Molecular Sciences Software Institute (MolSSI)
License: Apache License 2.0
MOPAC is written in Fortran. Learn Fortran with our recommended free books and free tutorials.
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