OpenMolcas
An open-source quantum chemistry suite focused on multiconfigurational electronic structure, excited states, spin–orbit effects and spectroscopy.
Where it fits
Photochemistry, transition-metal systems and problems requiring active-space methods.
Limits and practical considerations
Active-space and state-selection choices strongly affect results; specialist validation is essential.
Licensing and access
Open source, primarily distributed as source code; verify licence files for the chosen build and external components.