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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 is developed in the research group of Frank Neese. The free version is available only for academic use at academic institutions.


ORCA users should register, agree to the EULA , download and install a private copy of the program (via The free version is available only for academic use at academic institutions.


  • Download the ORCA 4.2.0, Linux, x86-64, shared-version, orca_4_2_0_linux_x86-64_shared_openmpi314.tar.xz
  • Move the downloaded file to your computing project's application area (/projappl/<proj>) on Puhti
  • Unpack the package (tar xf orca_4_2_0_linux_x86-64_shared_openmpi314.tar.xz)
  • Example parallel batch script for Puhti
#SBATCH --partition=small
#SBATCH --nodes=1
#SBATCH --ntasks-per-node=40
#SBATCH --account=<your billing project>
#SBATCH --time=0:30:00 # time as hh:mm:ss
#SBATCH --job-name=orca-4.2
#SBATCH --error=jobfile.err%J
#SBATCH --output=jobfile.out%J
module purge
module load intel/19.0.4 hpcx-mpi/2.4.0 intel-mkl/2019.0.4
export ORCADIR=<path to your ORCA directory>/orca_4_2_0_linux_x86-64_shared_openmpi314
$ORCADIR/orca orca_4.2.0.inp > orca_4.2.0.out


Please remember to adjust %pal nproc in your input file according to the total number of requested MPI tasks (nodes * ntasks-per-node)


Cite your work with the following references:

The generic reference for ORCA is: - Neese, F. (2012) The ORCA program system, Wiley Interdiscip. Rev.: Comput. Mol. Sci., 2, 73-78.

Please do not only cite the above generic reference, but also cite in addition the original papers that report the development and ORCA implementation of the methods you have used in your studies! The publications that describe the functionality implemented in ORCA are given in the manual.

Last edited Thu Oct 31 2019