ORCA is an ab initio quantum chemistry program package that contains 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.

ORCA requires a license per individual or research group (cf. or the ORCA forum Once you can proof that you are eligible, contact for activation of the ORCA module.

Availability / Target HPC systems

  • throughput cluster Woody and TinyEth/TinyFAT
  • owing to its limited scalability, ORCA is not suited for the parallel computers

New versions of ORCA are installed by RRZE upon request with low priority if the users provide the installation files.


  • orca has to be called with the full path otherwise parallel runs may fail.
  • The orca module will take care of loading an appropriate openmpi module, too.
  • ORCA often results in massive IO (“communication through files??”); thus, put temporary files into /dev/shm (RAM disk) or local scratch directory.

Sample job scripts

#!/bin/bash -l
#PBS -lnodes=1:ppn=4,walltime=10:00:00
#PBS -N my-orca
#PBS -j eo


module add orca/4.1.1

### No mpirun required as ORCA starts the parallel processes internally as needed.
### The number of processes is specified in the input file using '%pal  nprocs #  end'

${ORCABASE}/orca   orca.inp   "optional openmpi arguments"

Further information


  • please volunteer!