JUSTUS2/Software/Orca

The main documentation is available via module help chem/orca on the cluster. Most software modules for applications provide working example batch scripts.

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 Versions and Availability

On the command line interface of any bwHPC cluster you'll get a list of available versions by using the command
'module avail chem/orca'.

$ module avail chem/orca               # JUSTUS 2
------------------------------ ----------------/opt/bwhpc/common/modulefiles/Core --------------------------------------------------------
   chem/orca/4.2.1-xtb-6.3.3    chem/orca/5.0.1-xtb-6.4.1    chem/orca/5.0.2              chem/orca/5.0.3              chem/orca/5.0.4 (D)
   chem/orca/4.2.1              chem/orca/5.0.1              chem/orca/5.0.3-xtb-6.5.1    chem/orca/5.0.4_xtb-6.6.0

3 Usage

3.1 Loading the module

The most preferable way to load ORCA is with the specific version included, i.e., 'module load chem/orca/<version>'.

$ module load chem/orca/5.0.4

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.

3.2 Example Script

A working example of the submission script for a parallel ORCA job is available, after loading the module, at $ORCA_EXA_DIR/slurm_orca_example.sbatch file.

3.3 Miscellaneous

• To ensure successful parallel runs, it is necessary to call ORCA with the full path, i.e. '$ORCA_BIN_DIR/orca <input_file>'
• The ORCA module (accessible via 'module avail orca') automatically loads the appropriate OpenMPI module.
• 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 JUSTUS 2, please refer to the following link.

---