ORCA

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.

ORCA Available on the Cluster

Many versions of ORCA is available on our clusters. You can list all versions by ml av command.

$ ml av orca
-------------------------- /apps/modules/chem --------------------------
  ORCA/4_0_0-linux_x86-64    ORCA/4_0_1-linux_x86-64    ORCA/4.0.1.2 (D)

  Where:
   D:  Default Module

Serial Computation With ORCA

You can test serial computation with this simple input file. Create a file called orca_serial.inp and fill it with following ORCA commands.

    # Taken from the Orca manual
    # https://orcaforum.cec.mpg.de/OrcaManual.pdf
    ! HF SVP
    * xyz 0 1
      C 0 0 0
      O 0 0 1.13
    *

Next, create a PBS submission file (interactive job can be used too).

#!/bin/bash
#PBS -S /bin/bash
#PBS -N ORCA_SERIAL
#PBS -l select=1
#PBS -q qexp

ml ORCA/4.0.1.2
${EBROOTORCA}orca orca_serial.inp

Submit the job to the queue and wait before it ends. Then you can find an output log in your working directory.

$ qsub submit_serial.pbs
1417552.dm2

$ ll ORCA_SERIAL.*
-rw------- 1 hra0031 hra0031     0 Aug 21 12:24 ORCA_SERIAL.e1417552
-rw------- 1 hra0031 hra0031 20715 Aug 21 12:25 ORCA_SERIAL.o1417552

$ cat ORCA_SERIAL.o1417552

                                 *****************
                                 * O   R   C   A *
                                 *****************

           --- An Ab Initio, DFT and Semiempirical electronic structure package ---

                  #######################################################
                  #                        -***-                        #
                  #  Department of molecular theory and spectroscopy    #
                  #              Directorship: Frank Neese              #
                  # Max Planck Institute for Chemical Energy Conversion #
                  #                  D-45470 Muelheim/Ruhr              #
                  #                       Germany                       #
                  #                                                     #
                  #                  All rights reserved                #
                  #                        -***-                        #
                  #######################################################


                         Program Version 4.0.1.2 - RELEASE -

...

                             ****ORCA TERMINATED NORMALLY****
TOTAL RUN TIME: 0 days 0 hours 0 minutes 1 seconds 47 msec

Running ORCA in Parallel

Your serial computation can be converted to parallel in a very simple way. You simply have to specify the number of parallel processes by directive %pal. In this example, 4 nodes, 16 cores each are used.

Warning

Don't use ! PAL directive as only PAL2 to PAL8 is recognized!

    # Taken from the Orca manual
    # https://orcaforum.cec.mpg.de/OrcaManual.pdf
    ! HF SVP
    %pal
      nprocs 64 # 4 nodes, 16 cores each
    end
    * xyz 0 1
      C 0 0 0
      O 0 0 1.13
    *

You also need to edit the previously used PBS submission file. You have to specify number of nodes, cores and MPI-processes to run.

#!/bin/bash
#PBS -S /bin/bash
#PBS -N ORCA_PARALLEL
#PBS -l select=4:ncpus=16:mpiprocs=16
#PBS -q qexp

ml ORCA/4.0.1.2
${EBROOTORCA}/orca orca_parallel.inp

Note

When running ORCA in parallel, ORCA should NOT be started with mpirun: e.g. mpirun -np 4 orca etc. like many MPI programs and has to be called with full pathname.

Submit this job to the queue and see the output file.

$ qsub submit_parallel.pbs
1417598.dm2

$ ll ORCA_PARALLEL.*
-rw-------  1 hra0031 hra0031     0 Aug 21 13:12 ORCA_PARALLEL.e1417598
-rw-------  1 hra0031 hra0031 23561 Aug 21 13:13 ORCA_PARALLEL.o1417598

$ cat ORCA_PARALLEL.o1417598

                                 *****************
                                 * O   R   C   A *
                                 *****************

           --- An Ab Initio, DFT and Semiempirical electronic structure package ---

                  #######################################################
                  #                        -***-                        #
                  #  Department of molecular theory and spectroscopy    #
                  #              Directorship: Frank Neese              #
                  # Max Planck Institute for Chemical Energy Conversion #
                  #                  D-45470 Muelheim/Ruhr              #
                  #                       Germany                       #
                  #                                                     #
                  #                  All rights reserved                #
                  #                        -***-                        #
                  #######################################################


                         Program Version 4.0.1.2 - RELEASE -
...

           ************************************************************
           *        Program running with 64 parallel MPI-processes    *
           *              working on a common directory               *
           ************************************************************

...
                             ****ORCA TERMINATED NORMALLY****
TOTAL RUN TIME: 0 days 0 hours 0 minutes 11 seconds 859 msec

You can see, that the program was running with 64 parallel MPI-processes. In version 4.0.1.2, only the following modules are parallelized:

  • ANOINT
  • CASSCF / NEVPT2
  • CIPSI
  • CIS/TDDFT
  • CPSCF
  • EPRNMR
  • GTOINT
  • MDCI (Canonical-, PNO-, DLPNO-Methods)
  • MP2 and RI-MP2 (including Gradient and Hessian)
  • MRCI
  • PC
  • ROCIS
  • SCF
  • SCFGRAD
  • SCFHESS
  • SOC
  • Numerical Gradients and Frequencies

Register as a User

You are encouraged to register as a user of ORCA at Here in order to take advantage of updates, announcements and also of the users forum.

Documentation

A comprehensive PDF manual is available online.