Orca is a general purpose quantum chemistry program with emphasis in spectroscopy. It's free for academic use.
Written by Franck Neese et.al.
Methods included in version 2.6.35:
- Semiempirical AM1, PM3, ZINDO, NDDO, MNDO
- Hartree Fock theory (RHF, UHF, ROHF, CASSCF, SCS-MP2)
- DFT including double hybrid functionals
- Single reference: CCSD(T), QCISD(T), CEPA, CPF
- Multi-reference: MRCI, MRMP2, MRMP3, MRMP4, MRACPF, MRAQCC, SORCI
- Geometry optimization
- Excited state calculations via TD-DFT and CI-singles (CIS).
- Scalar relativistic ZORA, IORA and Douglas-Kroll-Hess (DKH)
- COSMO model for solvent
- Allows interface with existing QM/MM methods.
- Absorption and CD spectra from time-dependent DFT or MR-CI.
- EPR-parameters: Zero-Field Splittings, g-tensors, hyperfine couplings, quadrupole tensors from Hartree-Fock, DFT and MR-CI. Scalar relativistic corrections at the ZORA level.
- Mössbauer-parameters: isomer-shift and quadrupole splitting.
- Exchange coupling constants from broken-symmetry DFT (and pathway analysis) or Difference-dedicated CI (DDCI).
- NMR-parameters: chemical shifts from HF or DFT (but not with GIAO’s; IGLO is available)
- IR / RAMAN spectra, isotope shifts via numerical frequency calculations (HF and DFT)
- Simulation of absorption bandshapes and resonance-Raman excitation profiles from TD-DFT or MR-CI calculations
More information: https://orcaforum.cec.mpg.de