ORCA

Introduction

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.

Obtaining Access

According to the EULA, every user must register at the ORCA portal before obtaining access. As proof of this registration, users need to:

Take a screenshot of the page at https://www.faccts.de/customer/ with clearly visible name and links to download the ORCA software;
Take a screenshot of the registration confirmation email from the mailbox affiliated with your univerzity/institution;
Send both screenshots with your ORCA access request to support@it4i.cz.

After verifying your registration, you will be granted access to ORCA modules and executables.

Installed Versions

For the current list of installed versions, use:

$ ml av orca

Serial Computation With ORCA

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

    ! HF SVP
    * xyz 0 1
      C 0 0 0
      O 0 0 1.13
    *

Next, create a Slurm submission file for Karolina cluster (interactive job can be used too):

#!/bin/bash
#SBATCH --job-name=ORCA_SERIAL
#SBATCH --nodes=1
#SBATCH --partition=qcpu_exp
#SBATCH --time=1:00:00
#SBATCH --account=OPEN-0-0

ml ORCA/6.0.0-gompi-2023a-avx2
orca orca_serial.inp

Submit the job to the queue. After the job ends, you can find an output log in your working directory:

sbatch submit_serial.slurm
1417552

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

$ cat ORCA_SERIAL.o1417552

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

                #########################################################
                #                        -***-                          #
                #          Department of theory and spectroscopy        #
                #                                                       #
                #                      Frank Neese                      #
                #                                                       #
                #     Directorship, Architecture, Infrastructure        #
                #                    SHARK, DRIVERS                     #
                #        Core code/Algorithms in most modules           #
                #                                                       #
                #        Max Planck Institute fuer Kohlenforschung      #
                #                Kaiser Wilhelm Platz 1                 #
                #                 D-45470 Muelheim/Ruhr                 #
                #                      Germany                          #
                #                                                       #
                #                  All rights reserved                  #
                #                        -***-                          #
                #########################################################


                         Program Version 6.0.0  -   RELEASE  -

...

                             ****ORCA TERMINATED NORMALLY****
TOTAL RUN TIME: 0 days 0 hours 0 minutes 0 seconds 980 msec

Running ORCA in Parallel

Your serial computation can be easily converted to parallel. Simply specify the number of parallel processes by the %pal directive. In this example, 1 node, 16 cores are used.

Do not use the ! PAL directive as only PAL2 to PAL8 is recognized.

    ! HF SVP
    %pal
      nprocs 16
    end
    * xyz 0 1
      C 0 0 0
      O 0 0 1.13
    *

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


#!/bin/bash
#SBATCH --job-name=ORCA_PARALLEL
#SBATCH --nodes=1
#SBATCH --ntasks-per-node=16
#SBATCH --partition=qcpu_exp
#SBATCH --account=OPEN-0-0
#SBATCH --time=1:00:00

ml ORCA/6.0.0-gompi-2023a-avx2
$(which orca) orca_parallel.inp > output.out

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 a full pathname.

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

$ sbatch submit_parallel.slurm
Submitted batch job 2127305

$ cat output.out

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


                #########################################################
                #                        -***-                          #
                #          Department of theory and spectroscopy        #
                #                                                       #
                #                      Frank Neese                      #
                #                                                       #
                #     Directorship, Architecture, Infrastructure        #
                #                    SHARK, DRIVERS                     #
                #        Core code/Algorithms in most modules           #
                #                                                       #
                #        Max Planck Institute fuer Kohlenforschung      #
                #                Kaiser Wilhelm Platz 1                 #
                #                 D-45470 Muelheim/Ruhr                 #
                #                      Germany                          #
                #                                                       #
                #                  All rights reserved                  #
                #                        -***-                          #
                #########################################################


                         Program Version 6.0.0  -   RELEASE  -
...

           ************************************************************
           *        Program running with 16 parallel MPI-processes    *
           *              working on a common directory               *
           ************************************************************

...
                             ****ORCA TERMINATED NORMALLY****
TOTAL RUN TIME: 0 days 0 hours 0 minutes 17 seconds 62 msec

You can see, that the program was running with 16 parallel MPI-processes. In version 6.0.0, only the following modules are parallelized:

AUTOCI
CASSCF / NEVPT2 / CASSCFRESP
CIPSI
CIS/TDDFT
GRAD (general Gradient program)
GUESS
LEANSCF (memory conserving SCF solver)
MCRPA
MDCI (Canonical- and DLPNO-Methods)
MM
MP2 and RI-MP2 (including Gradients)
MRCI
PC
PLOT
PNMR
POP
PROP
PROPINT
REL
ROCIS
SCFGRAD
SCFRESP (with SCFHessian)
STARTUP
VPOT
Numerical Gradients, Frequencies, Overtones-and-Combination-Bands
VPT2
NEB (Nudged Elastic Band

Documentation

A comprehensive manual is available online.