Dr. Frank Wennmohs - ORCA

Dr. Frank Wennmohs
Head of Group ORCA
Department Molecular Theory and Spectroscopy

Group members


  • Ute Becker
  • Dagmar Lenk
  • Dr. Dimitrios Liakos
  • Kantharuban Sivalingam

ORCA - An ab initio, DFT and semiempirical SCF-MO package

To downlaod ORCA you have to register in the ORCA-Forum

The ORCA reference manual

Developer: Prof. Frank Neese

The program ORCA is a modern electronic structure program package written by F. Neese, with contributions from Ute Becker, Dmytro Bykov, Dmitry Ganyushin, Andreas Hansen, Robert Izsak, Dimitrios G. Liakos, Christian Kollmar, Simone Kossmann, Dimitrios A. Pantazis, Taras Petrenko, Christoph Reimann, Christoph Riplinger, Michael Roemelt, Barbara Sandhöfer, Igor Schapiro, Kantharuban Sivalingam, Frank Wennmohs, Boris Wezisla and contributions from our collaborators: Mihály Kállay, Stefan Grimme, Edward Valeev. The binaries of ORCA are available free of charge for academic users for a variety of platforms.

ORCA is a flexible, efficient and easy-to-use general purpose tool for quantum chemistry with specific emphasis on spectroscopic properties of open-shell molecules. It features a wide variety of standard quantum chemical methods ranging from semiempirical methods to DFT to single- and multireference correlated ab initio methods. It can also treat environmental and relativistic effects.

Due to the user-friendly style, ORCA is considered to be a helpful tool not only for computational chemists, but also for chemists, physicists and biologists that are interested in developing the full information content of their experimental data with help of calculations.

For a complete list of ORCA's capabilities, see our current reference manual.

New Features:

1) The parallelization of the program is now completed. All modules, including MRCI, are now parallel. Parallel performance has been improved in numerous cases.

2) A new module for performing efficient spin adpted single excitation configuration interaction calculations for open shell systems (ROCIS). This is particularly powerful for the calculation of transition metal L-edge X-ray absorption spectra. It is parallelized

3) A new module performing molecular dynamics calculations with ORCA. Also available for methods that only feature numerical gradients.

4) MDCI module:

  • Orbital optimized coupled cluster version for RHF and UHF (also parallelized)
  • Brückner coupled cluster (including triples) for RHF and UHF
  • SEIO functional for orbital invariant, stationary coupled pair calculations
  • Open shell LPNO-CEPA,QCISD and CCSD methods
  • Parameterized CCSD (pCCSD) in canonical and LPNO versions (RHF and UHF)


  • Relativistic CASSCF for the variational treatment of spin orbit coupling. Also uses symmetry.
  • Projection SOC states on spin-free states possible
  • Kramers restricted RELCAS
  • Numerous improvements in NEVPT2 (COSMO, Trajectories and scans, Direct-RI modeless storage)
  • Improved convergence and convergence aids (... but we are still working on this)
  • Spin-Spin coupling in QDPT CASSCF/NEVPT2 for magnetic properties
  • Determinant based full CI program added for the CI step


  • Fully parallelized including the QDPT procedure for magnetic properties

7) General/Misc. improvements

  • VDW10. Latest dispersion correction from the group of Grimme
  • Nonlocal DFT-NL for incorporation of dispersion in DFT
  • PW6 B95, PWP B95, RI-PWP B95 functionals
  • Rappoport/Furche optimized basis sets for properties
  • Basis set extrapolation now works also with def2 basis sets
  • Densities for interactive orca_plot
  • Differences and transition densities in orca_plot
  • Natural orbitals for unrelaxed MP2 density
  • SOS-MP2, SOS-RI-MP2, SOS-OO-RI-MP2 energies + gradients
  • DKH picture change for g-tensors
  • Overlap fitted RIJCOSX procedure leads to further speedups and improvements in accuracy
  • Libint2 for more efficient integral evaluation (uses contraction)
  • Parallelization of point charge correction for QM/MM
  • Interface to the MRCC program by Mihály Kállay

To the ORCA-forum

The ORCA reference manual