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 requires a license per individual or research group (cf. https://cec.mpg.de/orcadownload/ or the ORCA forum https://orcaforum.kofo.mpg.de/). Once you can proof that you are eligible, contact hpc-support@fau.de for activation of the ORCA module.

Availability / Target HPC systems

  • throughput cluster Woody and TinyFAT
  • owing to its limited scalability, ORCA is not suited for the parallel computers

New versions of ORCA are installed by RRZE upon request with low priority if the users provide the installation files.

Notes

  • orca has to be called with the full path otherwise parallel runs may fail.
  • The orca module will take care of loading an appropriate openmpi module, too.
  • ORCA often results in massive IO (“communication through files??”); thus, put temporary files into /dev/shm (RAM disk) or local scratch directory.

Sample job scripts

parallel orca on a Woody node 

#!/bin/bash -l
#SBATCH --nodes=1 
#SBATCH --ntasks-per-node=4
#SBATCH --time=01:00:00
#SBATCH --export=NONE

unset SLURM_EXPORT_ENV

cd $SLURM_SUBMIT_DIR

module add orca/5.0.3

### No mpirun required as ORCA starts the parallel processes internally as needed. 
### The number of processes is specified in the input file using '%pal nprocs # end' 

${ORCABASE}/orca orca.inp "optional openmpi arguments"

Further information

Mentors

  • please volunteer!