JUSTUS2/Software/Orca
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The main documentation is available via |
| Description | Content |
|---|---|
| module load | chem/orca/5.0.4 |
| Availability | bwUniCluster | JUSTUS2 |
| License | EULA |
| Citing | As described in the manual. Refer to Chapter 'Publications Related to ORCA' for guidance on citation. |
| Links | Main ORCA Forum Portal | Documentation |
| Graphical Interface | No |
1 Description
ORCA is a comprehensive, fully parallelized quantum chemistry package designed for advanced electronic structure methods. It encompasses density functional theory, many-body perturbation theory, coupled cluster methods, multireference methods, and semi-empirical quantum chemistry approaches. ORCA is capable of computing a wide range of molecular properties and serves as a fully integrated system for multi-level calculations, including QM/MM, ONIOM, and embedded crystals.
Additionally, ORCA offers several advanced features to improve computational efficiency and accuracy. These include local correlation methods, starting with PNOs and expanded to DLPNO to reduce the computational cost of coupled cluster calculations. It also incorporates RIJCOSX for efficient handling of Hartree-Fock based methods.
Furthermore, ORCA provides NEB-TS for studying reaction pathways and offers various methods for accurately calculating excited states, such as TD-DFT, EOM-CCSD, STEOM-CCSD, CASSCF with NEVPT2 or CASPT2, as well as molecular dynamics and multi-scale QM-MM models.
Please refer to documentation provided by the ORCA developers in the first place for more detailed information, e.g.:
Orca Manual 5.0.4
Article Overview by Frank Nesse
Article about main improvement in the version 5.0
2 Miscellaneous Notes to Usage
- ORCA utilizes MPI parallelization, specifically backed by OpenMPI. When configuring parallel jobs in the Slurm sbatch script, use appropriate directives such as --nodes and --ntasks-per-node.
Avoid using the --cpus-per-task directive. All the ORCA modules load the appropriate OpenMPI module automatically. - To ensure successful parallel runs, it is necessary to call ORCA with the full path, i.e. '$ORCA_BIN_DIR/orca <input_file>'
- Due to potential large I/O operations, especially for post HF methods, it is advisable to place temporary files a local scratch directory.
To learn more about local disk space on JUSTUS2, please refer to the $SCRATCH and $TMPDIR section on the "JUSTUS2 Hardware" page. - The most preferable way to load ORCA is with the specific version included, i.e., 'module load chem/orca/<version>'.
The default version, which may change over time, can be loaded simply with the command 'module load chem/orca'. - The module includes the loading of all additional modules, especially an appropriate OpenMPI module in the case of ORCA, necessary for the proper functioning of the program, so there's no need to load additional modules separately. However, loading additional modules may be counterproductive.
