The most widely used semi-empirical quantum mechanics program throughout the world.

MOPAC is a general-purpose semi-empirical quantum mechanics package for the study of chemical properties and reactions in gas, solution, or solid-state. MOPAC is used to directly predict numerous chemical and physical properties, such as Gibbs free energies, activation energies, reaction paths, dipole moments, non-linear optical properties, and infrared spectra. It is also used as the basis of quantitative structure-property (or activity) relationships, to predict a wide variety of biological and other properties including carcinogenicity, vapor pressure, water solubility, and reaction rates.
Use MOPAC to research:

• Macromolecules: very fast, patented, linear-scaling MOZYME algorithm optimizes proteins and DNA

A recent JACS paper suggests that active sites in enzymes correlate with the position of the frontier molecular orbitals (calculated on the "solvated" protein with MOPAC 2000 using the COSMO solvent model). See: Kazuki Ohno et al, J. Am. Chem. Soc. 2001, 123, 8161-8162. Effects of Hydration on the Electronic Structure of an Enzyme: Implications for Catalytic Function.

• Materials: d-orbitals, crystals, geometry in electric fields, NLO, 2D/3D periodic boundaries
• Polymers: band structures, phonon spectra, Young's modulus, tensile strength
• Dyes: MOS-F for UV spectra prediction, intersystem crossing, excited states in solution
• Synthesis: thermodynamics, kinetics, transition-states, reaction paths, solvation, catalysis

MOPAC 2006 Release Adds PM5:

• 4X Accuracy
  The new PM5 method improves accuracy up to 4X greater than PM3 and AM1 with new experimental data and algorithms.
• All Main Group Elements
  For the first time, all main group elements are included in one semi-empirical method - including Li, Be, B, Na, Mg, K, Ca, and more, opening up new areas of study such as biological systems.
• Transition Metals
  AM1-d provides more accurate geometries and heats of formation than current methods. For example, AM1-d heats of formation accuracies are comparable to PM3.
  
  
  
  
• *Heat of formation average unweighted errors compared to experiment.
• For a comparison between methods on a specific element, see our heat of formation comparison-by-element table.

Powerful Computer Engines

MOPAC includes the semi-empirical Hamiltonians MNDO, MINDO/3, AM1, PM3, MNDO-d, and PM5. These methods have been calibrated using experimental data for thermodynamic properties such as heats of formation.

Minutes instead of Days/Weeks

The patented MOZYME algorithms in MOPAC allow calculations that used to take days or weeks on a supercomputer to be performed in minutes on a Pentium-based personal computer. The electronic properties of systems with thousands of atoms, including proteins, polymers, semiconductors, and crystals can now be calculated in minutes instead of days or weeks.

System Requirements

• Suggested hardware configuration for Windows Version: Intel Pentium 4 2.0 Ghz or higher; 512 MB RAM or more; 500MB HDD space or more.
• Operating Systems : AIX(IBM), HP-UX, Fujitsu PrimePower, Windows98/NT/2000/XP and Linux