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orca website  

ORCA is an ab initio quantum chemistry program package for modern electronic structure methods including density functional theory, many-body perturbation, coupled cluster, multireference methods, and semi-empirical quantum chemistry methods. Its main field of application is larger molecules, transition metal complexes, and their spectroscopic properties. The program ORCA is developed in Frank Neese group, with contributions from many current and former coworkers and several collaborating groups. 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 the 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.

Environment Modules

Run module spider orca to find out what environment modules are available for this application.

System Variables

  • HPC_ORCA_DIR - installation directory

Additional Information

Questions about running ORCA or electronic structure methods in general should be addressed to Ajith Perera through the UFIT Support System Main Page. The following links are good resources:https://sites.google.com/site/orcainputlibrary/setting-up-orca and https://www.orcasoftware.de/tutorials_orca.

Job Script Examples

ORCA does not distribute the source code. The executable installed at Hipergator is built with OpenMPI 4.1.1 (the compiler is unspecified and assumed to be GNU/Linux x86_64). ORCA can run in parallel. However, there several important things that users need to know. ORCA calls mpirun internally, and most computer centers including Hipergator prefer mpirun (or srun with slurm controller) invoked externally. As the following example shows we are not using srun, instead directly call ORCA binary "orca" with the full path (essential!!). ORCA documentation does not give examples of how to use it with multiple nodes, there are many questions in ORCA forum https://orcaforum.kofo.mpg.de/app.php/portal about the problems users have when trying to run ORCA on multiple nodes. None of the suggested solutions seems to be satisfactory. After many trials and errors, I have found one that works, but it remains unclear to me how well ORCA performs on multiple nodes.See the ORCA_Job_Scripts page for orca Job script examples.


If you publish research that uses orca you have to cite it as follows: The ORCA quantum chemistry program package, Frank Neese, Ute Becker, Fran Wennmohs, Christoph Riplinger, J. Chem. Phys., 152, 224108 (2020).