MOPAC

MOPAC is primarily a serial command-line program. Its default behavior is to take a molecular geometry specified by an input file and perform a local optimization of the geometry to minimize the heat of formation of the molecule. The details of this process are then summarized by an output file. The behavior of MOPAC can be modified by specifying keywords on the first line of the input file, and translation vectors can be added to the geometry to specify a polymer, surface, or crystal.

MOPAC is compatible with other software to provide graphical user interfaces (GUIs), visualization of outputs, and processing of inputs. The most well-known GUIs that support MOPAC are  Chem3D, WebMO,{{cite web |title=WebMO |url=https://www.webmo.net}} the Amsterdam Modeling Suite,{{cite web |title=Amsterdam Modeling Suite |url=https://www.scm.com/amsterdam-modeling-suite/ |access-date=8 February 2024 |website=Software for Chemistry & Materials (SCM)}} and the Molecular Operating Environment. Jmol can visualize some MOPAC outputs such as molecular orbitals and partial charges. Open Babel supports conversion to and from MOPAC's input file format.

• Semiempirical models: AM1, PM3, PM6, PM7{{cite journal |last1=Stewart |first1=James J. P. |date=2012 |title=Optimization of parameters for semiempirical methods VI: more modifications to the NDDO approximations and re-optimization of parameters |journal=Journal of Molecular Modeling |volume=19 |issue=1 |pages=1–32 |doi=10.1007/s00894-012-1667-x|pmid=23187683 |pmc=3536963 }}
• Geometry optimization
• Transition-state optimization
• Vibrational analysis
• COSMO solvation model
• Periodic boundary conditions (Gamma point only, no Brillouin zone sampling)
• MOZYME for closed-shell systems (linear-scaling electronic structure algorithm)
• Gas-phase thermodynamics
• Molecular polarizability
• Automatic hydrogenation for pre-processing of Protein Data Bank structures
• INDO spectroscopy{{cite journal |last1=Gieseking |first1=Rebecca L. M. |date=2021 |title=A new release of MOPAC incorporating the INDO/S semiempirical model with CI excited states |journal=Journal of Computational Chemistry |volume=42 |issue=5 |pages=365–378 |doi=10.1002/jcc.26455|pmid=33227163 |url=https://chemrxiv.org/engage/api-gateway/chemrxiv/assets/orp/resource/item/60c74d9e842e6561a9db34cf/original/a-new-release-of-mopac-incorporating-the-indo-s-semiempirical-model-with-ci-excited-states.pdf }}
• Configuration interaction
• PARAM, a companion program for parameter optimization{{cite journal |last1=Stewart |first1=James J. P. |date=1989 |title=Optimization of parameters for semiempirical methods I. Method |journal=Journal of Computational Chemistry |volume=10 |issue=2 |pages=209–220 |doi=10.1002/jcc.540100208}}

MOPAC was originally developed in Michael Dewar's research group at the University of Texas at Austin to consolidate their previous developments of MINDO/3 and MNDO models and software and to serve as the software implementation of the AM1 model.{{cite journal |last1=Dewar |first1=Michael J. S. |title=Development of Practical MO Techniques for Prediction of the Properties and Behavior of Materials |url=https://apps.dtic.mil/sti/pdfs/ADA127029.pdf |journal=Air Force Office of Scientific Research Technical Report |volume=AFOSR-TR-83-0234 |access-date=8 February 2024}} The name MOPAC was both an acronym for Molecular Orbital PACkage and a reference to the Mopac Expressway that runs alongside parts of the UT Austin campus.{{cite web |author=J. J. P. Stewart |title=General Description of MOPAC |url=http://openmopac.net/manual/index.html |publisher=Stewart Computational Chemistry}} The first version of MOPAC was deposited in the Quantum Chemistry Program Exchange (QCPE) in 1983 as QCPE Program #455 with James Stewart as its primary author. James Stewart joined the Dewar group in 1980 as a visiting professor on leave from the University of Strathclyde,{{cite web |last1=Ramsey |first1=David |title=Jimmy Stewart offers logic of science to illogical Americans |url=https://gazette.com/news/jimmy-stewart-offers-logic-of-science-to-illogical-americans-david-ramsey/article_aad564aa-3e28-11ea-ad55-877599afb899.html |access-date=8 February 2024 |website=The Denver Gazette|date=23 January 2020 }} and he continued the development of MOPAC after moving to the United States Air Force Academy in 1984.{{cite web |last1=Hollingsworth |first1=Katherine |title=UGM Presenter Spotlight: James Stewart |url=https://www.materialsdesign.com/post/2019/09/06/ugm-presenter-spotlight-moritz-to-baben-1 |access-date=8 February 2024 |website=Materials Design, Inc.|date=6 September 2019 }} In 1993, MOPAC was acquired by Fujitsu and sold as commercial software, while James Stewart continued its development as a consultant.{{cite web |last1=Stewart |first1=James |title=Details of MOPAC-7 Release |url=http://www.ccl.net/cgi-bin/ccl/message.cgi?1992+10+26+004 |access-date=8 February 2024 |website=Computational Chemistry List}} After 2007, new versions of MOPAC were developed and sold by Stewart Computational Chemistry{{cite web |title=MOPAC |url=http://openmopac.net/ |access-date=8 February 2024 |website=Stewart Computational Chemistry (archived from 2007)|archive-url=https://web.archive.org/web/20071002182435/http://openmopac.net/ |archive-date=2007-10-02 }} with support from the Small Business Innovation Research program.{{cite web |title=Stewart, James awardee profile |url=https://www.sbir.gov/node/318133 |access-date=8 February 2024 |website=SBIR/STTR}} Concurrent with its commercial development, there was an effort to continue development of the last pre-commercial version of MOPAC as an open-source software project.{{cite web |title=mopac7 |url=https://sourceforge.net/projects/mopac7/ |access-date=9 February 2024 |website=SourceForge|date=22 June 2016 }}{{cite web |title=MOPAC version 7 (public domain) |url=https://github.com/jeffhammond/MOPAC |website=GitHub}} In 2022, the commercial development and distribution of MOPAC ended, and it was officially re-released as an open-source software project on GitHub{{cite web |title=MOPAC version 22.0.0 release |url=https://github.com/openmopac/mopac/releases/tag/v22.0.0 |access-date=8 February 2024 |website=GitHub}} developed by the Molecular Sciences Software Institute.{{cite web |title=Molecular Sciences Software Institute |url=https://molssi.org |access-date=8 February 2024}}

Early versions of MOPAC distributed by the QCPE were considered to be in the public domain and were forked into several other notable software projects. After James Stewart left, other members of the Dewar group continued to develop a fork of MOPAC called AMPAC that was originally released on the QCPE before also becoming commercial software.{{cite web |title=AMPAC 10 |url=http://www.semichem.com/ampac/ampac-new.php |website=Semichem, Inc.}} VAMP (Vectorized AMPAC) was a parallel version of AMPAC developed by Timothy Clark's group at the University of Erlangen–Nuremberg.{{cite book |last1=Clark |first1=Timothy |chapter=Molecular Orbital and Force-Field Calculations for Structure and Energy Predictions |date=1988 |title=Physical Property Prediction in Organic Chemistry |pages=95–102 |doi=10.1007/978-3-642-74140-1_9|isbn=978-3-642-74142-5 }} Donald Truhlar's group at the University of Minnesota developed both a fork of AMPAC with implicit solvent models, AMSOL,{{cite web |title=AMSOL Home Page |url=https://comp.chem.umn.edu/amsol/ |access-date=8 February 2024 |website=Chemical Theory Center, Department of Chemistry, University of Minnesota}} and a fork of MOPAC itself.{{cite web |title=MOPAC 5.022mn Home Page |url=https://comp.chem.umn.edu/mopac/ |access-date=8 February 2024 |website=Chemical Theory Center, Department of Chemistry, University of Minnesota}} Also, commercial versions of MOPAC distributed by Fujitsu have some proprietary features (e.g. PM5, Tomasi solvation) not available in other versions.{{cite web |title=MOPAC 2002 |url=http://www.cachesoftware.com/mopac/index.shtml |access-date=8 February 2024 |website=CAChe Software (archived)|archive-url=https://web.archive.org/web/20040807015509/http://www.cachesoftware.com/mopac/index.shtml |archive-date=2004-08-07 }}

MOPAC used different versioning systems throughout its development, sometimes with a version number or year stylized into the name. These alternate names include MOPAC3, MOPAC4, MOPAC5, MOPAC6, MOPAC7, MOPAC93, MOPAC97, MOPAC 2000, MOPAC 2007, MOPAC 2009, MOPAC 2012, and MOPAC 2016.{{cite web |title=MOPAC archive |url=https://github.com/openmopac/mopac-archive |access-date=8 February 2024 |website=GitHub}} Open-source versions of MOPAC now use semantic versioning.

• List of quantum chemistry and solid-state physics software
• Semi-empirical quantum chemistry methods
• AMPAC

{{Reflist}}

• [http://openmopac.net/Download_MOPAC_Executable_Step2.html MOPAC download page on openmopac.net]
• [https://github.com/openmopac/mopac-archive Historical archive of MOPAC source code and manuals]
• [https://web.archive.org/web/20050416091523/http://www.cachesoftware.com/mopac/Mopac2002manual/ MOPAC 2002 Manual]
• [http://openmopac.net/manual/index.html MOPAC 2009 Manual]
• Source code and compiled binaries at the Computational Chemistry List repository:
• Source code (in FORTRAN):
• [http://www.ccl.net/cca/software/SOURCES/FORTRAN/mopac6_sources/index.shtml MOPAC 6]
• [http://www.ccl.net/cca/software/SOURCES/FORTRAN/mopac7_sources/index.shtml MOPAC 7]
• Compiled binaries:
• [http://www.ccl.net/cca/software/MS-DOS/mopac_for_dos/mopac6/index.shtml MOPAC 6] for MS-DOS/Windows;
• [http://www.ccl.net/cca/software/MS-WIN95-NT/mopac6/index.shtml MOPAC 6] for Windows 95/NT;
• MOPAC 6 with GUI ([https://web.archive.org/web/20091126133822/http://winmostar.com/index_en.html Winmostar])
• [http://www.ccl.net/cca/software/MS-DOS/mopac_for_dos/mopac7/index.shtml MOPAC 7] for MS-DOS/Windows
• [http://www.ccl.net/cca/software/LINUX/mopac7/index.shtml MOPAC 7] for Linux
• [http://comp.chem.umn.edu/mopac/ MOPAC-5.022mn (MOPAC at the University of Minnesota)]

{{Chemistry software}}

Category:Computational chemistry software