PyQuante
- "Python Quantum Chemistry" - an open-source suite of programs for developing quantum chemistry methods. Emphasis is on simplicity, rather than speed, but some bottlenecks are written in C.
- http://pyquante.sourceforge.net/

GAMESS-UK
- Free program derived from the original GAMESS code.
- http://www.cse.clrc.ac.uk/qcg/gamess-uk/

Motofit
- Co-refines Neutron and X-ray reflectometry data, using Parratt recursion and least squares fitting. It works in the IGOR Pro environment (TM Wavemetrics).
- http://motofit.sourceforge.net

MPQC
- The "Massively Parallel Quantum Chemistry Program". Computes properties of atoms and molecules from first principles using the time independent Schrödinger equation. Free, available under the GPL.
- http://www.mpqc.org/

ORCA
- Ab initio, DFT and semiempirical SCF-MO package, with specific emphasis on spectroscopic properties of open-shell molecules. Free binaries for academic users are available for a variety of platforms.
- http://ewww.mpi-muelheim.mpg.de/bac/logins/downloads_en.php

Banned By Gaussian
- Site critical of Gaussian, Inc.'s licensing practices. Reports allegations of Gaussian banning "competitors" from using their product.
- http://www.bannedbygaussian.org/

CHEMKED
- Chemical kinetics of gas phase reactions. Databases, simulation, and analysis software for Windows. Demo version available.
- http://mark.jelezniak.de/Chemked/

Atoms in Molecules (AIM2000)
- Windows program for analyzing and visualizing molecules using the theory of Richard Bader. Demo version available.
- http://www.aim2000.de

SHB_interactions
- Free program based on Extended Hückel calculations and Mulliken overlap populations for measuring the strength of hydrogen bonds and other intermolecular interactions in drug-biopolimer complexes.
- http://gw-chimie.math.unibuc.ro/staff/cbendic/shb/shb_interactions.html

Zori
- Open source quantum chemistry program for atoms and molecules using the quantum Monte Carlo method.
- http://www.zori-code.com/

CASTEP - CAmbridge Serial Total Energy Package
- Uses density functional theory to provide an atomic-level description of materials and molecules.
- http://www.tcm.phy.cam.ac.uk/castep/

Moloc
- Molecular Design Software Suite for Irix, Linux, and Windows. Includes features such as structure generation, molecular mechanics, conformational search, molecular dynamics, and similarity analysis. Free for academic users.
- http://www.moloc.ch/

WinMopac
- Free graphical version of MOPAC 7 for windows, with an integrated molecular viewer (RasWin). Used for semiempirical molecular orbital calculations with the MNDO, AM1, and PM3 methods.
- http://www.psu.ru/science/soft/winmopac/index_e.html

AOMix
- A program for molecular orbital analysis. It calculates the MO compositions of the constituent chemical fragments from the output files of various quantum-chemical packages, analyzes chemical bonding using overlap populations, and generates density-of-sta
- http://www.sg-chem.net/

Environment-Dependent Interatomic Potential (EDIP)
- Codes in C and Fortran by Martin Z. Bazant to model interatomic forces in covalent solids and liquids which incorporates recent theoretical advances in understanding the environment-dependence of (sigma) chemical bonding in condensed phases.
- http://www-math.mit.edu/~bazant/EDIP/

CHEAQS
- Free windows program for calculating chemical equilibria in aquatic systems. CHEAQS solves speciation problems and includes a customizable database of equilibrium constants.
- http://home.tiscali.nl/cheaqs

GaussSum
- Collection of Python scripts which parse the output of Gaussian or GAMESS calculations to extract information such as the progress of the SCF cycles, geometry optimisation, UV-Vis/IR/Raman spectra, MO levels, and MO contributions.
- http://gausssum.sourceforge.net/

Extensible Computational Chemistry Environment
- Graphical user interface for Linux/Solaris/IRIX with visualization tools and a data management framework for setting up, submitting, and analyzing computational chemistry calculations.
- http://ecce.emsl.pnl.gov/

CRYSTAL Home Page
- Unix program to compute the electronic structure of periodic systems within Hartree Fock, density functional or various hybrid approximations. Documentation, licensing, and downloads available.
- http://www.crystal.unito.it/

CONFLEX2000
- Commercial conformational searching and analysis tools for Linux, Mac OS X, and Windows. Compatible w/CAChe, ChemOffice, and Amber. Screen shots, data sheet, ordering, and trial versions available.
- http://www.conflex.us/

YAeHMOP
- "Yet Another extended Huckel Molecular Orbital Package". Performs calculations and visualization for both molecular and extended materials in 1, 2, or 3 dimensions. Freely available in source form.
- http://yaehmop.sourceforge.net/

ArgusLab
- A free molecular modeling program for Windows9x operating systems with 3D-builder, various ab initio calculation modules and simple molecular mechanics.
- http://www.planaria-software.com/

Gamess
- An ab initio quantum chemistry package GAMESS. Developed by the Mark Gordon research group at Iowa State University. Site is not GAMESS-Uk.
- http://www.msg.ameslab.gov/GAMESS/GAMESS.html

Zeta Potential
- Zeta is a free (GPL) computer program which can be used to calculate the zeta potentials.
- http://zeta-potential.sourceforge.net/

WebMO
- Web interface for the quantum chemistry packages MOPAC, Gaussian, and GAMESS. Free version available for download; pro version also available.
- http://www.webmo.net/

Spectra
- Windows program for the interactive analysis of crystal field spectra of f-block elements.
- http://chemistry.anl.gov/downloads/spectra/

Jaguar
- A general purpose ab initio electronic structure package that is capable of computing variety of properties based on various uncorrelated and correlated wavefunctions.
- http://www.schrodinger.com/Products/jaguar.html

MOMix and ALP-Vibro
- Programs for Quantum Chemistry. MOMix (electron population analysis). ALP-vibro (animation of molecular vibrations). Spectrum Wizard.
- http://www.chem.yorku.ca/grad/SG/momix.htm

MOLCAS
- Program for an accurate ab initio treatment of very general electronic structure problems for molecular systems in both ground and excited states. Online manuals, billboard and patches for MOLCAS.
- http://www.teokem.lu.se/molcas/

ADF
- ADF, the Amsterdam Density Functional program for the treatment of complex chemical problems.
- http://www.scm.com

CHEMKIN Collection Software
- Simulates complex chemical kinetics in reacting flow.
- http://www.chemkin.com/