ORCA

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.

From Wikipedia

!!! Attention

ORCA requires all users to create an account on their forum board before
executables can be downloaded. Moreover, each executable is linked to a
specific version of OpenMPI, so a containerized solution is usually
ideal for running on Perlmutter.

[Link to Orca Forum](https://orcaforum.kofo.mpg.de/app.php/portal)

Support

ORCA users can seek support via the Orca forum.

Install ORCA

The steps below describe how to install the static MPI version of ORCA 5.0.4.

Download Compressed Files

The ORCA binaries are precompiled and released in several tarballs available to download from their forum. Since the total size of the ORCA package is so large (~40 GB), we recommend that you install it on our filesystems rather than inside a container image. For long-term use, we suggest you install them on our /global/common/software filesystem. You may need to request a quota increase first because the default quotas can be small on this filesystem. You can do this by filling out the Disk Quota Increase Form.

Extract Compressed Files to a Single Directory

From the directory containing the downloaded tarballs, extract the contents into a single folder. You can use the following commands to do this after substituting /your/install/path/orca for the path where you would like to install ORCA.

mkdir -p /your/install/path/orca for file in orca_5_0_4_linux_x86-64_openmpi411_part[1-3].tar.xz; do \ tar -xvf "$file" -C /your/install/path/orca; \ mv /your/install/path/orca/${file%%.*}/* /your/install/path/orca/; \ rm -r /your/install/path/orca/${file%%.*}; \ done

ORCA is precompiled, so once the files have been extracted, it is ready to use.

Running ORCA

ORCA is coded to use OpenMPI version 4.1.1 and its drive code contains calls to mpirun, therefore we recommend running in a container. Moreover, it’s not necessary to call the ORCA executable itself with srun or mpirun. Below is a table of containers suited for running ORCA.

Containers for ORCA

OpenMPI ver.	Repository	ORCA version
4.1.1	docker.io/stephey/orca:3.0	5.0.4

Test Example for Multiprocess Runs

This is an example ORCA input file, named input_parallel.inp, that contains directives to run an analysis using 16 MPI processes.

!HF DEF2-SVP %PAL NPROCS 16 END %MAXCORE 1000 %SCF MAXITER 500 END * xyz 0 1 O 0.0000 0.0000 0.0626 H -0.7920 0.0000 -0.4973 H 0.7920 0.0000 -0.4973 *

Single-Node Batch Job

To run the above example on a single node, the batch script below can be used:

```

!/bin/bash

SBATCH -q run

SBATCH -N 1

SBATCH -n 16

SBATCH -c 16

SBATCH -t 00:20:00

SBATCH -C cpu

SBATCH –image=stephey/orca:3.0

Prepare Environment

export PATH=/your/install/path/orca:$PATH export PATH=/usr/bin:$PATH export LD_LIBRARY_PATH=/usr/lib:$LD_LIBRARY_PATH

Prepare Working Directory

mkdir -p ORCA_workdir cp input_parallel.inp ./ORCA_workdir/input_parallel.inp cd ORCA_workdir

Run ORCA

shifter /your/install/path/orca /your/install/path/orca/ORCA_workdir/input_parallel.inp “–bind-to core” ```

Notes

With this configuration, it is only possible to run on a single node.
Ensure that the number of NPROCS in the input file matches the number of MPI tasks (-n) selected in the job script.
If you are using the nprocs_group option for grouping parallel tasks, please use "--bind-to none" instead of the "--bind-to core" option. Binding each task to a single core in this case may result in ORCA running with fewer than the desired number of MPI tasks.

Multi-Node Batch Job

!!! warning

The following directions use OpenMPI version 5.0. This method is not recommended
by ORCA developers.

Although ORCA depends on OpenMPI version 4.1.1, some functionality can be obtained using the OpenMPI version 5.0 module provided by NERSC. Below is an example job script that demonstrates a multinode run:

```

!/bin/bash

SBATCH -q regular

SBATCH -N 2

SBATCH -n 16

SBATCH –ntasks-per-node=8