ORCA

ORCA is a general-purpose quantum chemistry program package that features virtually all modern electronic structure methods (density functional theory, many-body perturbation and coupled cluster theories, and multireference and semiempirical methods). It is designed with the aim of generality, extendibility, efficiency, and user friendliness. Its main field of application is larger molecules, transition metal complexes, and their spectroscopic properties

Please note that ORCA does not currently support GPU acceleration. Therefore, when utilizing ORCA on our HPC cluster, it is essential to optimize job scripts and resource allocation for CPU-based calculations to achieve optimal performance.

Running ORCA jobs

To run ORCA on the HPC cluster, you need to load the appropriate software module:

flight env activate gridware
module load apps/ORCA/5.0.4
module load mpi/openmpi/4.0.7

Below is an example of a job script and input file for running a basic ORCA calculation:

!/bin/bash

#SBATCH --job-name=orca-test
#SBATCH --nodes=1
#SBATCH --tasks-per-node=4
#SBATCH --time=1:00:00
#SBATCH --partition=nodes

export UCS_LOG_LEVEL=error

flight env activate gridware
module load apps/orca/5.0.4
module load mpi/openmpi/4.0.7

input=input.inp

$ORCADIR/orca ${input} > ${input}.out 2>&1

In the example, the job is submitted to the CPU queue (--partition=nodes). It reserves 4 cores for 1 hour.

The input file (input.inp):

! DLPNO-CCSD(T) cc-pVTZ cc-pVTZ/C cc-pVTZ/jk rijk verytightscf TightPNO LED
# Specify number of processors
%pal
nprocs 4
end
# Specify memory
%maxcore 12000
%mdci
printlevel 3
end
* xyz 0 1
O 1.327706 0.106852 0.000000
H 1.612645 -0.413154 0.767232
H 1.612645 -0.413154 -0.767232
O -1.550676 -0.120030 -0.000000
H -0.587091 0.053367 -0.000000
H -1.954502 0.759303 -0.000000
*
%geom
Fragments
2 {3:5} end
end
end