Orca

Description

Orca is a quantum chemistry software from the Max-Planck-Institut für Kohlenforschung.

Getting access to orca

The main developer of ORCA, Prof. Frank Neese, has changed the ORCA end user license agreement (EULA) for versions 4.0 and newer, such that it does no longer allow computer centers at academic institutions (like the ETH data center, where the Euler is located) to provide a central ORCA installation without access restriction. The new EULA enforces that all users need to register at the ORCA portal:

https://orcaforum.kofo.mpg.de/app.php/portal

After registering, you can use the command get-access orca that will check for the existence of your ORCA account and give you access to it if it succeeds.

Available versions on Euler

Version	Module load command
5.0.4	module load stack/2024-06 openmpi/4.1.1 orca/5.0.4
6.0.0	module load stack/2024-06 openmpi/4.1.1 orca/6.0.0
6.0.1	module load stack/2024-06 openmpi/4.1.1 orca/6.0.1
6.1.0	module load stack/2024-06 openmpi/4.1.6 orca/6.1.0

How to submit a job

You need to use the full path to the orca binary, when calling the software, otherwise the job will fail (see https://orca-manual.mpi-muelheim.mpg.de/contents/calling.html#hints-on-the-use-of-parallel-orca)

sbatch [Slurm options] --wrap="$(which orca) input.inp > output.out"

alternatively, you can use a jobscript

Parallel jobs

Please note that it is not sufficient to request multiple cores from the batch system to run orca in parallel. You also need to specify in the input file how many cores should be used

%pal nprocs 4

The example would specify that orca can use 4 cores.

Example input file

# Input file for the goldchloride example:
! BP ECP{def2-TZVP,def2-TZVP/J} def2-tzvp def2-tzvp/j tightscf opt
%pal nprocs 4
end
* xyz -2 2
Au  0   0   0
Cl  2.5 0   0
Cl -2.5 0   0
Cl  0   2.5 0
Cl  0  -2.5 0
*