The program ORCA is a modern electronic structure program package written by Prof. 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.
The List of new ORCA features you will find here.


<span>18.01.2016: </span><span>Introduction to ORCA. Installation, first calculation, and how to analyze the results. Useful calculation advice.</span>

Frank Wennmohs, „Introduction to ORCA program system“

18.01.2016: Introduction to ORCA. Installation, first calculation, and how to analyze the results. Useful calculation advice.


Bismuth is the heaviest of the stable elements - all subsequent elements are radioactive.

To be able to exploit the advantages of elements and their molecular compounds in a targeted manner, chemists have to develop a fundamental understanding of their properties. In the case of the element bismuth, a team from the Max Planck Institut für Kohlenforschung has now taken an important step. more

Prof. Frank Neese, director at the Max-Planck-Institut für Kohlenforschung

The Max-Planck-Institut für Kohlenforschung is delighted about the great response to the work of its scientists - for example Prof. Frank Neese, Director of the Department of Molecular Theory and Spectroscopy. more

Frank Neese is one of the "Highly Cited Researchers".

Frank Neese is once again honored as “Highly Cited Researcher” more

<p>The ORCA 5.0 Release is finally here!</p>

Introductory talk and presentation of new features on July 1st and 2nd more

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ORCA Referenz Manual

For more information commercial users are referred to:

ORCA is supported by the NOMAD repository

For questions regarding ORCA licensing, please contact:

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