What is MOPAC?

From the MOPAC manual:

MOPAC 93 is a general-purpose semiempirical molecular orbital package for the study of solid state and molecular structures and reactions.
The semiempirical Hamiltonians MNDO, MNDO/3, AM1, and PM3 are used in the electronic part of the calculation to obtain molecular orbitals, the heat of formation and its derivative with respect to molecular geometry.
Using these results MOPAC calculates the vibrational spectra, thermodynamic quantities, isotopic substitution effects and force constants for molecules, radicals ions and polymers.
For studying chemical reactions, a transition state location routine and two transition state optimizing routines are available.
While MOPAC calls upon many concepts in quantum theory and thermodynamics and uses some fairly advanced mathematics, the user need not be familiar with these specialized topics. MOPAC is written with the non-theoreticianin mind. The input data are kept as simple as possible, so users can give their attention to the chemistry involved and not concern themselves with quantum and thermodynamic exotica.
The simplest description of how MOPAC works is that the user creates a data-file which describes a molecular system and specifies what kind of calculations and output are desired. The user then commands MOPAC to carry out the calculation using that data-file. Finally the user extracts the desired output on the system from the output files created by MOPAC.
Summary of MOPAC 93 capabilities

• MNDO, MINDO/3, AM1, and PM3 Hamiltonians
  
• Restricted Hartree-Fock (RHF) and Unrestricted Hartree-Fock (UHF) methods
  
• Extensive Configuration Interaction
  
  • By default, up to 100 configurations
    
  • Singlets, Doublets, Triplets, Quartets, Quintets, and Sextets
    
  • Exited states
    
  • Geometry optimizations, etc., on specified states
    
• Single SCF calculation
  
• Geometry optimization
  
• Dradient minimization
  
• Transition state location
  
• Reaction path coordinate calculation
  
• Force constant calculation
  
• Normal coordinate analysis
  
• Transition dipole calculation
  
• Thermodynamic properties calculation
  
• Localized orbitals
  
• Non-linear Optical properties
  
• Solution-phase effects
  
• Solid-state phenomena
  
• Covalent bond orders
  
• Bond analysis into sigma and pi contributions
  
• One, two, and three dimensional solid-state calculations
  
• Dynamic Reaction Coordinate calculation
  
• Intrinsic Reaction Coordinate calculation
  

Last updated on August 22nd, 1996