ORCA is a flexible, efficient and easy-to-use general purpose tool for quantum chemistry with specific emphasis on spectroscopic properties of open-shell molecules. It features a wide variety of standard quantum chemical methods ranging from semiempirical methods to DFT to single- and multireference correlated ab initio methods. It can also treat environmental and relativistic effects. For more information, see

ORCA users should register, agree to the EULA , download and install a private copy of the program (via )

  1. Download the ORCA 4.1.1, Linux, x86-64, shared-version
  2. Transfer the downloaded file to Taito
  3. Unpack the program to $USERAPPL
    • tar xf orca_4_1_1_linux_x86-64_shared_openmpi313.tar.xz -C $USERAPPL


Version on CSC's Servers

  • Taito: 4.1.1


module load orca-env/4.1.1

An example job file can be copied from /appl/chem/orca/orca_4.1.1.job (orca_4.1.1.inp) .
Please remember to adjust %pal nproc in your input file according to the  --ntasks ( --ntasks-per-node ) in your jobfile

At present, Orca jobs works only if they are executed within an single node, see the Orca forum "running ORCA 4.1.1 ompi 313 across the nodes under SLURM"





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 (pages 756-782)