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OpenThermo is a program package for statistical thermodynamics computations beyond rigid rotor harmonic oscillator approximation (RRHOA), with taking into account internal rotations and vibration anharmonicity.

Such calculations often require individual approach for every molecule, and their difficulty rapidly increase with taking more factors into consideration. OpenThermo provides the user with the set of tools for processing different molecular data to the thermodynamic functions. In contrast to statistical subprograms integrated to QC packages, OpenThermo is designed to make the calculation transparent to user and give maximum control under the choice of used theories and approximations. OpenThermo is the first program package intended solely for statistical thermodynamics computations, available for public.

Starting from the version 1.0 Beta 1 package uses new XML-based format of input files. It became more user-friendly and requires input of less data amount than in previous versions, assuming other to be default.

Navigation: • OpenThermoDownloadInstallationUser's ManualDeveloper's ManualLicenseLinks


Latest Release (June 2009)

OpenThermo 1.0 Beta 1 was released. Packages for Windows and Linux as well as the source code are available for download. Review Release Notes for information about what is new in the latest release. Roadmap for future development of OpenThermo is available here

Report a bug... Request a feature...

Getting Started manual for OpenThermo 1.0 Beta 1 is available here.
Full User's Manual hasn't been completed yet, please look through the examples provided with the program.

What is OpenThermo

Do You Need OpenThermo?

Do you...

  • break your mind with the Pitzer tables?
  • evaluate huge statistical expressions with calculator?
  • find tremendous analytical expressions for first and second derivatives of post-RRHO partition function?
  • still tolerate GAUSSIAN's slowlyness because of its thermodynamical capabilities?
  • want to learn statistical thermodynamics on practical examples?

If you have answered "yes" on one or more questions, you definitely need OpenThermo!

Current OpenThermo 1.0 Beta 1 Capabilities

  • evaluation of heat capacities Cv(T) and Cp(T), entropy S0(T), energy
    U0(T)-U0(0), enthalpy H0(T)-H0(0), free energy F0(T)-F0(0), free enthalpy
    G0(T)-G0(0) and zero-point vibrational energy (ZPVE) from molecular geometry,
    list of vibrational frequencies and description of internal rotations;
  • treatment of rotations as free or hindered in quantum or classic approaches;
  • automatic symmetry analysis for molecule and internal rotors;
  • automatic Fourier interpolation of discreetly defined potential bariers;
  • calculations with anharmonic correction (require anharmonic (experimental or
    scaled) vibrational frequencies);
  • verbose log file makes thermodynamic calculation more transparent to user.

OpenThermo Limitations

OpenThermo package was written with large non-linear molecules in mind, so it lacks some useful features related to mono-,diatomic and linear molecules:

  • OpenThermo cannot work with monoatomic gases
  • OpenThermo cannot calculate partition function with interaction of rotations and vibrations


  • OpenThermo has no capabilities for treatment of condensed states

Unfortunately, this fields lay outside sphere of my scientific interests. If you are researcher and you are interested in such functionality, you can join the project and help with their implementation.

Who Wrote OpenThermo?

OpenThermo was developed by Konstantin L. Tokarev. You may contact him via e mail: annulen_at_users_sourceforge_dot_net.

Author would like to acknowledge these people for valuable advices and ideas:

Marat F. Fazylbekov
Aleksander Kuznetsov
Aleksander V. Abramenkov
Alexey Voskov
Andrey V. Stolyarov
Max Topchiy

This program has been made better thanks to the existence of open source software. Specifically, it relies on the work of :

  • Sergey Patchkovskii, author of Brute force symmetry analyzer

(original version is available on http://www.cobalt.chem.ucalgary.ca/ps/symmetry)

  • Robert B. Davies, author of Newmat library


  • Michael Fink and Karl Pitrich, authors of xmlpp,

non-validating XML Parser (http://xmlpp.sourceforge.net/)

GUI for OpenThermo

Although I've tried to make input file OpenThermo convenient for user, GUI is required by some users. GUI project is started on GitHub (http://github.com/annulen/openthermo-qt4). Your contributions will be highly appreciated.


If you'd like to take part in OpenThermo development, write to e-mail annulen_at_users_sourceforge_dot_net (Konstantin Tokarev), or look for posts in 'Help needed' section on SourceForge.

If you found OpenThermo useful and you'd like to see it with new features and calculation methods, please, make a donation to support develpment of OpenThermo.

Navigation: • OpenThermoDownloadInstallationUser's ManualDeveloper's ManualLicenseLinks

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