Dirac

General
Dirac represents a four-component relativistic quantum chemistry program for calculations of molecular energies with SCF, DFT, MP2, CI, or CC wave functions, analytic gradients and response functions at the SCF level, and numerical gradients at the MP2 and CC levels. The code adopts a symmetry scheme that provides maximum molecular point group (in D2h and subgroups) and time reversal symmetry reduction of the computational effort. See the official homepage for details.

Policy
The Dirac quantum chemistry program is available to users at NSC under the condition that published work includes citation of the program (see below) as well as citations to papers describing the implementation in cases when certain features of the code have been used.

Program citation
"Dirac, a relativistic ab initio electronic structure program, Release DIRAC04.0 (2004)", written by H. J. Aa. Jensen, T. Saue, and L. Visscher with contributions from V. Bakken, E. Eliav, T. Enevoldsen, T. Fleig, O. Fossgaard, T. Helgaker, J. Laerdahl, C. V. Larsen, P. Norman, J. Olsen, M. Pernpointner, J. K. Pedersen, K. Ruud, P. Salek, J. N. P. van Stralen, J. Thyssen, O. Visser, and T. Winther. (http://dirac.chem.sdu.dk)

Manual
A manual is available on the official homepage .

Essentials
To run Dirac one has to provide it with two input files called xxxx.inp and yyyy.mol where xxxx and yyyy are arbitrary strings. The yyyy.mol file typically contains information about the molecular symmetry, nuclear coordinates, and the basis functions. The xxxx.inp file contains information about the approximation to be used (Hartree-Fock, MP2, etc.) and what molecular properties should be calculated. When executing Dirac one types:

pam yyyy xxxx

As a result a file called xxxx_yyyy.out will be produced. A sample of input and output files is found below for respective platform.

Resource specifics

• Monolith
• Mozart
• Green

Dirac on Monolith
To run Dirac on Monolith with use of 4 processors (2 nodes with 2 processors each) for 1 hour, submit the shell script below to the queue (the submit command is: qsub scriptname). The input files xxxx.inp and yyyy.mol are assumed to be located in the submit directory. Temporary files created by the program are placed on the node local disk named /disk/local in order not to slow down the network file system (NFS), and the temporary files are removed after the calculation is completed. See output file.

#!/bin/bash
#PBS -l walltime=01:00:00
#PBS -l nodes=2:ppn=2

PAMPATH=/usr/local/chem/dirac/Dirac04/Dirac

dir=xxxx
mol=yyyy

NProc=`wc -l < $PBS_NODEFILE`
cd $PBS_O_WORKDIR
time $PAMPATH/pam -mpi $NProc $mol $dir
#
# End of script
#

Dirac on Mozart
To set the shell environment so that Dirac can be executed on Mozart, you need to add the Dirac module. Therefore, before the first use of Dirac, type

echo "dirac" > $HOME/.modules

To run Dirac on Mozart with use of 4 processors for 1 hour, submit the shell script below to the queue (the submit command is: qsub scriptname). The input files xxxx.inp and yyyy.mol are assumed to be located in the submit directory. Temporary files created by the program are placed on the disk named /scratch/$USER, and the temporary files are removed after the calculation is completed. See output file.

#!/bin/bash
#PBS -l walltime=1:00:00
#PBS -l nodes=1:ppn=4

NProc=`wc -l < $PBS_NODEFILE`

dirinp=xxxx
molinp=yyyy

cd $PBS_O_WORKDIR
time $PAM -mpi $NProc $molinp $dirinp

#
# End of script
#

Dirac on Green
To run Dirac on Green with use of 4 processors for 1 hour, submit the shell script below to the queue (the submit command is: qsub scriptname). The input files xxxx.inp and yyyy.mol are assumed to be located in the submit directory. Temporary files created by the program are placed on the node local disk named /disk/local in order not to slow down the network file system (NFS), and the temporary files are removed after the calculation is completed. See output file.

#!/bin/bash
#PBS -l walltime=01:00:00
#PBS -l nodes=4

PAMPATH=/usr/local/chem/dirac/Dirac04

dir=xxxx
mol=yyyy

NProc=`wc -l < $PBS_NODEFILE`
cd $PBS_O_WORKDIR
time $PAMPATH/pam -mpi $NProc $mol $dir
#
# End of script
#