Molcas 8.4

Molcas is an ab initio quantum chemistry software package developed by scientists to be used by scientists. The basic philosophy is is to be able to treat general electronic structures for molecules consisting of atoms from most of the periodic table. As such, the primary focus of the package is on multiconfigurational methods with applications typically connected to the treatment of highly degenerate states.

Molcas code is based on a stable version of OpenMolcas. In contrary to Molcas, which comes with support and verified release, OpenMolcas is a developer's branch, which integrity is verified by automatic tests.

Key aspects of Molcas:

  • Fast, accurate, and robust code
  • Free support and updates
Molcas is not a black box tool. The user should be an educated quantum chemist, with some knowledge about the different quantum chemical models in use today, their application areas and their inherent accuracy. The MOLCAS group arranges regular MOLCAS workshops, which teaches how to use the software.

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  • 2021-06-16. if you experience problems with installation - edit sbin/ file and change (last line) http:// to https://
  • Important note for Mac users. If you upgraded MacOS to version 10.15, molcas driver says: "Bad CPU type in executable”. Remove bin/molcas.exe and start make to download 64-bit executable
  • 190705 Service pack 1 for Molcas 8.4 is available!
    At users download page it possible to download Molcas84 (Note! a valid licence is required) and binaries for standard serial and parallel installations and special installations (compiled with Chem2PS and QCMaquis).
  • 190615 Molcas 8.4 is available!
    To obtain the source code, send e-mail to
  • 160919 New book Multiconfigurational Quantum Chemistry
  • If you would like to join Molcas developer's team, submit your project here.