PyQuante is an open-source (BSD) suite of programs for developing quantum chemistry methods using Gaussian type orbital (GTO)

Gaussian orbital

In computational chemistry and molecular physics, Gaussian orbitals are functions used as atomic orbitals in the LCAO method for the computation of electron orbitals in molecules and numerous properties that depend on these.- Rationale :The principal reason for the use of Gaussian basis functions...

 basis sets

Basis set (chemistry)

A basis set in chemistry is a set of functions used to create the molecular orbitals, which are expanded as a linear combination of such functions with the weights or coefficients to be determined. Usually these functions are atomic orbitals, in that they are centered on atoms. Otherwise, the...

. The program is written in the Python

Python (programming language)

Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...

 programming language, but has many "rate-determining" modules also written in C

C (programming language)

C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

 for speed, and also uses and requires the NumPy linear algebra extensions to Python. The resulting code, though not as fast as other quantum chemistry programs, is much easier to understand and modify. The goal of this software is not necessarily to provide a working quantum chemistry program (although it will hopefully do that), but rather to provide a well-engineered set of tools so that scientists can construct their own quantum chemistry programs without going through the tedium of having to write every low-level routine.

Current PyQuante Features

• Hartree–Fock: restricted closed-shell and unrestricted open-shell implementations;
• Density functional theory
  Density functional theory
  Density functional theory is a quantum mechanical modelling method used in physics and chemistry to investigate the electronic structure of many-body systems, in particular atoms, molecules, and the condensed phases. With this theory, the properties of a many-electron system can be determined by...
  
  : LDA
  Local-density approximation
  Local-density approximations are a class of approximations to the exchange-correlation energy functional in density functional theory that depend solely upon the value of the electronic density at each point in space . Many approaches can yield local approximations to the XC energy...
  
   (SVWN, Xalpha) and GGA (BLYP) functionals;
• Optimized-effective potential method for orbital-dependent density functional approximations;
• Two electron integrals computed using Huzinaga, Rys, or Head-Gordon
  Martin Head-Gordon
  Martin Philip Head-Gordon is a professor of chemistry at the University of California, Berkeley, and Lawrence Berkeley National Laboratory working in the area of computational quantum chemistry. He is a member of The International Academy of Quantum Molecular Science.A native of Australia,...
  
  /Pople
  John Pople
  Sir John Anthony Pople, KBE, FRS, was a Nobel-Prize winning theoretical chemist. Born in Burnham-on-Sea, Somerset, England, he attended Bristol Grammar School. He won a scholarship to Trinity College, Cambridge in 1943. He received his B. A. in 1946. Between 1945 and 1947 he worked at the Bristol...
  
   techniques; C
  C (programming language)
  C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
  
   and Python
  Python (programming language)
  Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
  
   interfaces to these programs;
• MINDO
  MINDO
  MINDO, or Modified Intermediate Neglect of Differential Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Intermediate Neglect of Differential Overlap method of John Pople. It was developed by the group...
  
  /3 semiempirical energies and forces;
• CI
  Configuration interaction
  Configuration interaction 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. Mathematically, configuration simply describes the linear combination...
  
  -singles excited states;
• DIIS
  DIIS
  DIIS , also known as Pulay mixing, is an extrapolation technique...
  
   convergence acceleration;
• Second-order Møller–Plesset perturbation theory (MP2).

See also

• PyQuante SourceForge Site, which contains more information and download links.
• PyQuante is written and maintained by Rick Muller.

• List of quantum chemistry and solid state physics software