MOPAC is a

computational chemistry Computational chemistry is a branch of chemistry that uses computer simulations to assist in solving chemical problems. It uses methods of theoretical chemistry incorporated into computer programs to calculate the structures and properties of mol ...

software package that implements a variety of

semi-empirical quantum chemistry methods Semi-empirical quantum chemistry methods are based on the Hartree–Fock formalism, but make many approximations and obtain some parameters from empirical data. They are very important in computational chemistry for treating large molecules where t ...

based on the neglect of diatomic differential overlap (NDDO) approximation and fit primarily for gas-phase

thermochemistry Thermochemistry is the study of the heat energy which is associated with chemical reactions and/or phase changes such as melting and boiling. A reaction may release or absorb energy, and a phase change may do the same. Thermochemistry focuses on ...

. Modern versions of MOPAC support 83 elements of the

periodic table The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods") and columns (" groups"). It is an icon of chemistry and is widely used in physics and other s ...

(H-La, Lu-Bi as atoms, Ce-Yb as

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

ic ''sparkles'') and have expanded functionality for solvated molecules, crystalline solids, and

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, re ...

. MOPAC was originally developed in Michael Dewar's research group in the early 1980s and released as

public domain The public domain (PD) consists of all the creative work to which no Exclusive exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly Waiver, waived, or may be inapplicable. Because no one holds ...

software on the Quantum Chemistry Program Exchange in 1983. It became commercial software in 1993, developed and distributed by Fujitsu, and Stewart Computational Chemistry took over commercial development and distribution in 2007. In 2022, it was released as open-source software on GitHub.

Functionality

MOPAC is primarily a serial

command-line A command-line interface (CLI) is a means of interacting with software via commands each formatted as a line of text. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternativ ...

program. Its default behavior is to take a

molecular geometry Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that det ...

specified by an input file and perform a local optimization of the geometry to minimize the

heat of formation In chemistry and thermodynamics, the standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements in their reference state, wi ...

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 A graphical user interface, or GUI, is a form of user interface that allows user (computing), users to human–computer interaction, interact with electronic devices through Graphics, graphical icon (computing), icons and visual indicators such ...

(GUIs), visualization of outputs, and processing of inputs. The most well-known GUIs that support MOPAC are Chem3D, WebMO, the Amsterdam Modeling Suite, and the Molecular Operating Environment.

Jmol Jmol is computer software for molecular modelling of chemical structures in 3 dimensions. It is an open-source Java viewer for chemical structures in 3D. The name originated from ''Jva (the programming language) + olcules, and also the m ...

can visualize some MOPAC outputs such as

molecular orbitals In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of finding ...

and

partial charges In atomic physics, a partial charge (or net atomic charge) is a non-integer charge value when measured in elementary charge units. It is represented by the Greek lowercase delta (𝛿), namely 𝛿− or 𝛿+. Partial charges are created due to ...

. Open Babel supports conversion to and from MOPAC's input file format.

Major features

* Semiempirical models: AM1, PM3, PM6, PM7 * Geometry optimization * Transition-state optimization * Vibrational analysis * COSMO solvation model * Periodic boundary conditions (Gamma point only, no

Brillouin zone In mathematics and solid state physics, the first Brillouin zone (named after Léon Brillouin) is a uniquely defined primitive cell in reciprocal space Reciprocal lattice is a concept associated with solids with translational symmetry whic ...

sampling) * MOZYME for closed-shell systems (linear-scaling electronic structure algorithm) * Gas-phase

thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed b ...

* Molecular polarizability * Automatic

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...

for pre-processing of

Protein Data Bank The Protein Data Bank (PDB) is a database for the three-dimensional structural data of large biological molecules such as proteins and nucleic acids, which is overseen by the Worldwide Protein Data Bank (wwPDB). This structural data is obtained a ...

structures * INDO spectroscopy *

Configuration interaction Configuration interaction (CI) is a post-Hartree–Fock linear variational method for solving the nonrelativistic Schrödinger equation within the Born–Oppenheimer approximation for a quantum chemical multi-electron system. Mathemati ...

* PARAM, a companion program for parameter optimization

History

MOPAC was originally developed in Michael Dewar's research group at the

University of Texas at Austin The University of Texas at Austin (UT Austin, UT, or Texas) is a public university, public research university in Austin, Texas, United States. Founded in 1883, it is the flagship institution of the University of Texas System. With 53,082 stud ...

to consolidate their previous developments of MINDO/3 and

MNDO MNDO, or Modified Neglect of Diatomic Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Neglect of Diatomic Differential Overlap integral approximation. ...

models and software and to serve as the software implementation of the AM1 model. The name ''MOPAC'' was both an

acronym An acronym is a type of abbreviation consisting of a phrase whose only pronounced elements are the initial letters or initial sounds of words inside that phrase. Acronyms are often spelled with the initial Letter (alphabet), letter of each wor ...

for ''Molecular Orbital PACkage'' and a reference to the Mopac Expressway that runs alongside parts of the UT Austin campus. 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 The University of Strathclyde () is a public research university located in Glasgow, Scotland. Founded in 1796 as the Andersonian Institute, it is Glasgow's second-oldest university, having received its royal charter in 1964 as the first techn ...

, and he continued the development of MOPAC after moving to the

United States Air Force Academy The United States Air Force Academy (USAFA) is a United States service academies, United States service academy in Air Force Academy, Colorado, Air Force Academy Colorado, immediately north of Colorado Springs, Colorado, Colorado Springs. I ...

in 1984. In 1993, MOPAC was acquired by Fujitsu and sold as commercial software, while James Stewart continued its development as a consultant. After 2007, new versions of MOPAC were developed and sold by Stewart Computational Chemistry with support from the Small Business Innovation Research program. 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. In 2022, the commercial development and distribution of MOPAC ended, and it was officially re-released as an open-source software project on GitHub developed by the Molecular Sciences Software Institute. 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. VAMP (Vectorized AMPAC) was a parallel version of AMPAC developed by Timothy Clark's group at the

University of Erlangen–Nuremberg The Friedrich-Alexander University of Erlangen-Nuremberg (, FAU) is a Public University, public research university in the cities of Erlangen and Nuremberg in Bavaria, Germany. The name Friedrich-Alexander is derived from the university's first ...

Donald Truhlar Donald Gene Truhlar (born 27 February 1944, Chicago) is an American scientist working in theoretical and computational chemistry and chemical physics with special emphases on quantum mechanics and chemical dynamics. Early life, education, and ea ...

's group at the

University of Minnesota The University of Minnesota Twin Cities (historically known as University of Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Twin Cities of Minneapolis and Saint ...

developed both a fork of AMPAC with implicit solvent models, AMSOL, and a fork of MOPAC itself. Also, commercial versions of MOPAC distributed by Fujitsu have some proprietary features (e.g. PM5, Tomasi solvation) not available in other versions. 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. Open-source versions of MOPAC now use

semantic versioning Software versioning is the process of assigning either unique ''version names'' or unique ''version numbers'' to unique states of computer software. Within a given version number category (e.g., major or minor), these numbers are generally assig ...

References

External links

MOPAC download page on openmopac.net

Historical archive of MOPAC source code and manuals

MOPAC 2002 Manual

*

Source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...

and compiled

binaries A binary file is a computer file that is not a text file. The term "binary file" is often used as a term meaning "non-text file". Many binary file formats contain parts that can be interpreted as text; for example, some computer document files ...

at the Computational Chemistry List repository: ** Source code (in FORTRAN): *
MOPAC 6
**
MOPAC 7
** Compiled binaries: **
MOPAC 6
for

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

; **
MOPAC 6
for

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...

/ NT; *** MOPAC 6 with GUI
Winmostar
**
MOPAC 7
for MS-DOS/Windows **
MOPAC 7
for

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

MOPAC-5.022mn (MOPAC at the University of Minnesota)
{{Chemistry software Computational chemistry software

Functionality

Major features

History

See also

References

External links