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ORCA is a general purpose tool for quantum chemistry with specific emphasis on spectroscopic properties of open-shell molecules. It features a wide variety of standard quantum chemical methods ranging from semiempirical methods to DFT to single- and multireference correlated ab initio methods. It can also treat environmental and relativistic effects.


To use the application you first need to accept its licence.

For Orca version 3.0.1 click here

For Orca version 4.x.x and above click here

License: https://orcaforum.kofo.mpg.de/app.php/privacypolicy/policy


Upcoming modulesystem change alert!

Due to large number of applications and their versions it is not practical to keep them explicitly listed at our wiki pages. Therefore an upgrade of modulefiles is underway. A feature of this upgrade will be the existence of default module for every application. This default choice does not need version number and it will load some (usually latest) version.

You can test the new version now by adding a line

source /cvmfs/software.metacentrum.cz/modulefiles/5.1.0/loadmodules

to your script before loading a module. Then, you can list all versions of orca and load default version of orca as

module avail orca/ # list available modules
module load orca   # load (default) module

If you wish to keep up to the current system, it is still possible. Simply list all modules by

module avail orca

and choose explicit version you want to use.

Manuals (as pdf files) for actual versions are placed in /cvmfs/software.metacentrum.cz/spack1/software/orca/.

Notes on usage

Notice: This application supports parallel computing (MPI, OpenMP) which can have weird consequences. For more details about parallel computing visit the page Parallelization.

You should always run the Orca program with it's full path because it's finding the program parts according to the run path. Example:

$(which orca) input

or directly

/software/orca-3.0.1/bin/orca in.inp
/software/orca/4.2.1/orca in.inp

Newer versions of Orca (> 5.0*) are prepared using the Spack package manager and the directory structure is different

#example for module orca/orca-5.0.1-intel-19.0.4-bnofsgq
/cvmfs/software.metacentrum.cz/spack1/software/orca/linux-debian10-x86_64/5.0.1-intel-bnofsg/bin/orca in.inp

OpenMPI computing

Don't try to run mpirun -np $NCPUs orca. ORCA will take care of it if you have the !PAL keyword set.

Use with NAMD

NAMD uses Orca application for some computation. However due to different installation methods usually both programs use different OpenMPI to run. In Orca-4.2.1 module is created a wrapper for 'orca' binary to avoid OpenMPI mismatch problems. Now should be sufficient to put the path to this orca wrapper to NAMD configuration file and avoid of running 'module add orca-4.2.1' in your PBS script. For documentation purposes, the wrapper is this:

 eval $(env |sed -n '/^OMPI/s/^\([^=]*\).*/unset \1;/p')
 module add orca-4.2.0
 exec /software/orca/4.2.1/orca "$@"