Orca

module avail orca/

Orca is a general purpose tool for quantum chemistry with specific emphasis on spectroscopic properties of open-shell molecules.

Orca 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.

Usage

License

To use the application, you first need to accept its licence:

• Orca version 3.0.1
• Orca version 4.x.x and above

Notes

Docs

User reference manuals (as pdf files) are placed in /cvmfs/software.metacentrum.cz/spack1/software/orca/.

Path specification

You should always run the Orca program with its full path because it finds 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

Some of the newer versions of Orca (typically > 5.0) are prepared using the Spack package manager, and the directory structure is different

# example for module 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.

Usage with NAMD

NAMD uses the Orca application for some computation. However, due to different installation methods, both programs usually use different OpenMPI to run.

In the Orca-4.2.1 module is created a wrapper for orca binary to avoid OpenMPI mismatch problems. Now, it should be sufficient to put the path to this orca wrapper to the NAMD configuration file and avoid running module add orca/4.2.1 in your PBS script. For documentation purposes, the wrapper is this:

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