Q-Chem
A molecular electronic-structure suite spanning DFT, correlated wavefunction methods, excited states, solvation and chemical reaction calculations.
Where it fits
Molecular spectroscopy, open-shell electronic states and reaction energetics.
Limits and practical considerations
Check method-specific gradients, parallel support and optional module entitlements.
Licensing and access
Commercial licensing with annual, permanent and maintenance options; a vendor-issued licence file is required.
Official documentation and project