ORCA 2016

Introduction

The program ORCA is a modern electronic structure program package that is able to carry out geometry optimizations and to predict a large number of spectroscopic parameters at different levels of theory. Besides the use of Hartee Fock theory, density functional theory (DFT) and semiempirical methods, high level ab initio quantum chemical methods, based on the configuration interaction and coupled cluster methods, are included into ORCA to an increasing degree.

For more details please refer the offical home of ORCA where you can also find a thorough documentation on using the program. Note that ORCA is free of charge for non-commercial use and by using ORCA on the cluster you are accepting the ORCA license. In particular, any scientific work using ORCA should at least cite

F. Neese: The ORCA program system (WIREs Comput Mol Sci 2012, 2: 73-78)

as well as other related works as apropriate.

Below, a short introduction to using ORCA on the cluster is given.

Installed version

The currently installed versions of ORCA are 3.0.3 and 4.0.0:

You can always check that out by yourself, you only need to use the command "module av ORCA":

$ module av ORCA

------------------------ /cm/shared/uniol/modules/chem -------------------------
   ORCA/3.0.3    ORCA/4.0.0 (D)

  Where:
   D:  Default Module

Using ORCA on the HPC cluster

You have to prepare a jobscript and an inputfile for your ORCA job. An example ORCA-job could look like this:

#SBATCH --partition=carl.p
#SBATCH --time=1-00:00:00
#SBATCH --mem=2G 
#SBATCH --job-name ORCA-TEST
#SBATCH --output=slurm-%j.out
#SBATCH --error=slurm-%j.err 
module load ORCA
MODEL=TiF3
ORCAEXE=`which orca`
$ORCAEXE ${MODEL}.inp > ${MODEL}.out

The first 5 lines are meant for SLURM. In the first line configuring the time needed for the job. Please be as accurate as possible but keep in mind that the job will fail if, e.g. the time is set to 1 hour but the job actually needs 5 hours. Second line defines the memory. For this job 2G (2Gb) should be enough. After that, we need to name our job, our example job is named "ORCA-TEST". The following two lines are defining the output- and the errorfile. Without adding these two lines, the output and errors will be saved into a single file.

Documentation

The full documentation of the most recent version of ORCA (currently 4.0.0) can be found here (PDF viewer required).