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ORCA

Description

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.

The ORCA home page is at https://orcaforum.cec.mpg.de.

Available modules

Packages with modules

Module NeSI Cluster
ORCA/4.0.1-OpenMPI-2.0.2 pan
ORCA/3_0_3-linux_x86-64 pan
ORCA/4.0.0-OpenMPI-2.0.2 pan
ORCA/4.0.0.2-OpenMPI-2.0.2 pan

Licensing requirements

ORCA is released as precompiled binaries at no cost, pursuant to a closed-source licence which is available at https://orcaforum.cec.mpg.de/license.html. Users are advised that the terms of the ORCA licence allow its use in the course of academic research only, and that each research group is expected to register with the ORCA developers. If you have any questions regarding your eligibility to access ORCA or any particular version of it, please contact our support desk.

Example scripts

Example scripts for the Pan cluster

Basic usage

#!/bin/bash -e

#SBATCH --job-name      ORCA_job
#SBATCH --account       nesi99999
#SBATCH --time          01:00:00
#SBATCH --ntasks        16  # or fewer. ORCA is inefficient with ntasks > 16
#SBATCH --mem-per-cpu   4G
#SBATCH --output        ORCA_job.%j.out # Include the job ID in the names
#SBATCH --error         ORCA_job.%j.err # of the output and error files

module load ORCA/3_0_3-linux_x86-64
orca_exe=$(which orca)

# Note that ORCA should not be run through "srun", even when being executed
# as an MPI process.
${orca_exe} MyInput.inp

Advanced usage with fast temporary disk

#!/bin/bash -e

#SBATCH --job-name       ORCA_job
#SBATCH --account        nesi99999
#SBATCH --time           01:00:00
#SBATCH --ntasks         16  # or fewer. ORCA is inefficient with ntasks > 16
#SBATCH --mem-per-cpu    4G
#SBATCH --output         ORCA_job.%j.out # Include the job ID in the names
#SBATCH --error          ORCA_job.%j.err # of the output and error files

module load ORCA/3_0_3-linux_x86-64
orca_exe=$(which orca)

# We use ${CHK_DIR} instead of ${SCRATCH_DIR} so that the GBW file is
# preserved in the event that the job crashes or is killed by the scheduler.
thisdir=$(pwd -P)
workdir="${CHK_DIR}/${SLURM_JOB_NAME}-${SLURM_JOB_ID}"
mkdir -p "${workdir}"
inputfile="MyInput.inp"
cp "${inputfile}" "${workdir}/."

# Go to the temporary working directory within ${CHK_DIR}
cd "${workdir}"

${orca_exe} "${inputfile}"

# Delete temporary files and the temporary copy of the input file
rm -rfv *.tmp "${inputfile}"

# Copy all remaining files back to the starting directory, removing them from
# the working directory if the copy succeeds
for file in *
do
    cp -arv --no-preserve=mode "${file}" "${thisdir}" && rm -rfv "${file}"
done

cd "${thisdir}"

Further notes

Requesting a parallel run

ORCA requires a parallel run to be requested in its input as well as from the batch scheduler. To request a parallel run, you need to add a line to the input file like the following:

%pal nprocs <np> end

where <np> represents the total number of processors (cores) you have requested from the scheduler.

Checkpointing and restarting

ORCA provides for saving of checkpoint data, especially molecular orbital information, in a file with extension ".gbw" (short for Geometry-Basis-Wavefunction). Given an input file name of "foo.inp" or some equivalent, the GBW file will be named "foo.gbw". It appears that the GBW file, like temporary and other output files, will be written in the same directory from which the ORCA executable is invoked.

To restart from an existing GBW file, you should do the following:

  1. Ensure that the GBW file you want to start from is renamed so that it does not have the same base name as your intended input file. Otherwise, it will be overwritten and destroyed as soon as ORCA starts running.
  2. In your input file, specify the following lines, replacing "checkpoint.gbw" with the name of the GBW file you intend to read from:
! moread
% moinp "checkpoint.gbw"
  1. Run the calculation.

For more information about restarting from an older GBW file, including how to restart from GBW files produced using earlier versions of ORCA, please consult the ORCA manual.

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