.. _dirac:


=====
DIRAC
=====

.. contents:: In this section:
   :local:
   :depth: 2

Description
===========

According to the `page of DIRAC <http://www.diracprogram.org/>`_, the DIRAC program calculates molecular properties using relativistic quantum chemical methods. It is named after P.A.M. Dirac, the father of relativistic electronic structure theory.

Available Versions
==================

* dirac/12.3-mpi (default)
* dirac/12.3-serial
* dirac/12.3-smp

Serial Job Submission
=====================

.. code-block:: bash
   :caption: submit_dirac_serial.sh

   #!/bin/bash
   #SBATCH -J dirac_serial
   #SBATCH -N 1
   #SBATCH -n 1
   #SBATCH -t 05:00:00
   #SBATCH --mem=8G

   export INPUT="methanol.xyz hf.inp"
   export OUTPUT="*.out *..."

   module load dirac/12.3-serial

   job-nanny pam --dirac=$DIRAC_EXEC --scratch=/tmp \
                 --mol=methanol.xyz --inp=hf.inp

SMP (OpenMP) Job Submission
===========================

.. code-block:: bash
   :caption: submit_dirac_smp.sh

   #!/bin/bash
   #SBATCH -J dirac_smp
   #SBATCH -N 1
   #SBATCH -c 4
   #SBATCH -t 08:00:00
   #SBATCH --mem=16G

   export INPUT="methanol.xyz hf.inp"
   export OUTPUT="*.out *..."
   export OMP_NUM_THREADS=$SLURM_CPUS_PER_TASK

   module load dirac/12.3-smp

   job-nanny pam --dirac=$DIRAC_EXEC_SMP --scratch=/tmp \
                 --mol=methanol.xyz --inp=hf.inp

MPI Job Submission
==================

.. code-block:: bash
   :caption: submit_dirac_mpi.sh

   #!/bin/bash
   #SBATCH -J dirac_mpi
   #SBATCH -N 2
   #SBATCH --ntasks-per-node=28
   #SBATCH -t 24:00:00
   #SBATCH --mem-per-cpu=2G

   export INPUT="methanol.xyz hf.inp"
   export OUTPUT="*.out *..."

   module load dirac/12.3-mpi

   job-nanny mpirun -np $SLURM_NTASKS pam --dirac=$DIRAC_EXEC_MPI \
                     --scratch=/store --mol=methanol.xyz --inp=hf.inp

.. important::
   For MPI jobs, use ``--scratch=/store`` to have shared space between nodes.

Example Input File
==================

.. code-block:: text
   :caption: hf.inp

   **DIRAC
   .TITLE
   Methanol HF calculation
   .WAVE FUNCTIONS
   **WAVE FUNCTIONS
   .SCF
   *SCF
   .CLOSED SHELL
   9
   **HAMILTONIAN
   .DEFAULT
   **INTEGRALS
   *READIN
   .DEFAULT
   **MOLECULE
   *BASIS
   .DEFAULT
   cc-pVDZ
   *READIN
   .DEFAULT
   **END OF

Coordinates File (XYZ)
======================

.. code-block:: text
   :caption: methanol.xyz

   6
   Methanol molecule
   C   0.0000   0.0000   0.0000
   O   0.0000   0.0000   1.4280
   H   0.9860   0.0000  -0.4960
   H  -0.4390  -0.8510  -0.4960
   H  -0.4390   0.8510  -0.4960
   H   0.8510   0.0000   1.8860

Job Array for Multiple Molecules
================================

.. code-block:: bash
   :caption: submit_dirac_array.sh

   #!/bin/bash
   #SBATCH -J dirac_array
   #SBATCH --array=1-5
   #SBATCH -N 1
   #SBATCH -c 4
   #SBATCH -t 12:00:00
   #SBATCH --mem=16G

   MOLECULES=(
       "methanol"
       "ethanol"
       "water"
       "ammonia"
       "benzene"
   )

   MOL=${MOLECULES[$SLURM_ARRAY_TASK_ID-1]}
   export INPUT="${MOL}.xyz ${MOL}.inp"
   export OUTPUT="${MOL}_results/"
   export OMP_NUM_THREADS=$SLURM_CPUS_PER_TASK

   module load dirac/12.3-smp

   mkdir -p ${MOL}_results
   cd ${MOL}_results
   cp ../${MOL}.xyz .
   cp ../${MOL}.inp .

   job-nanny pam --dirac=$DIRAC_EXEC_SMP --scratch=/tmp \
                 --mol=${MOL}.xyz --inp=${MOL}.inp

References
==========

- Documentation: http://www.diracprogram.org/doc/release-17/
- Manuals: http://www.diracprogram.org/doc/release-17/manual/
- Tutorials: http://www.diracprogram.org/doc/release-17/tutorials/

.. seealso::

   - :ref:`gamess` - Alternative for quantum chemistry
   - :ref:`gaussian` - Alternative for quantum chemistry
   - :ref:`running_simulations` - How to submit jobs