ORCA
A molecular quantum chemistry package combining DFT, correlated single- and multireference methods, spectroscopy and molecular reaction-path tools.
Where it fits
Molecular energetics, transition-metal chemistry and spectroscopic interpretation.
Limits and practical considerations
Approximate local-correlation settings and method-specific convergence still require validation.
Licensing and access
Free for qualifying academic and personal use; commercial licences are supplied by FACCTs. Not an unrestricted open-source licence.