ORCA

ORCA is a flexible, efficient and easy-to-use 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.

Policy

ORCA is available to users at HPC2N who has a license.

ORCA is and will remain free for academic and personal use. ORCA requires each user to register, (see ORCA forum), and send the confirmation mail to support@hpc2n.umu.se.

After the confirmation mail has been received by “support@hpc2n.umu.se” the user will be added to the ORCA group in SUPR (supr.naiss.se) and access to the ORCA installation at HPC2N will be granted.

NOTE: the confirmation mail we need has the subject “Confirmation ORCA Registration”

Citations

See “How to cite” for how to include acknowledgement of the use of this program into scientific papers.

Overview

ORCA is a powerful and versatile quantum chemistry software package, primarily developed by the group of Prof. Frank Neese. It is free for academic use, while commercial licenses are available through FACCTs. ORCA is also the computational engine inside our workflow tool WEASEL.

  • Cutting edge
    • ORCA provides cutting-edge methods in the field of electronic structure theory, including density functional- as well as correlated wave function-based methods.
    • With a strong user base of more than 67000 registered users in academia worldwide, ORCA is the fastest-growing quantum chemistry software package to date.
  • Fast & accurate
    • We put great effort in making accurate calculations as fast as possible, and ORCA is known to be among the fastest quantum chemistry codes.
    • Some developments such as the DLPNO and RIJCOSX schemes can speed up calculations by orders of magnitude and even lead to a linear-scaling increase in timing with respect to system size.
  • Complete
    • ORCA is a multi-purpose quantum chemistry software package. It features a wide variety of methods ranging from semi-empirical methods to density functional theory to correlated single- and multi-reference wave function-based methods. Environmental as well as relativistic effects can be taken into account.
    • We have the leading software tool in the calculation of molecular properties, and offer a native molecular dynamics module as well as a native QM/MM module for large-scale systems.
  • Easy-to-use
    • ORCA is designed and developed with attention to both users and their teams. Computational chemists and physicists work hand in hand with spectroscopists and bench chemists to develop a software that is suited and beneficial for all.

Usage at HPC2N

On HPC2N we have ORCA available as a module. Users need to have registered for a license at https://orcaforum.kofo.mpg.de/ (free).

Loading

To use the ORCA module, add it to your environment. You can find versions with 

module spider ORCA

and you can then find how to load a specific version (including prerequisites), with 

module spider ORCA/<VERSION>

Running

Note

ORCA requires that one specifies the full path to the binary when starting.

For ORCA version 4 one must always use

$EBROOTORCA/orca

when starting it.

For ORCA version 5 one must always use 

$EBROOTORCA/bin/orca

Submit file example

Regardless of running a serial job or a parallel (MPI) job, the binary to use is “orca”. It will internally start the sub-parts and if “nprocs” is > 1 in the input file it will use MPI versions and will handle the MPI startup. So the only submit file you need is:

#!/bin/bash
#SBATCH -A hpc2nXXXX-YYY
#SBATCH -n 8
#SBATCH -t 01:00:00

ml purge > /dev/null 2>&1
ml GCC/8.3.0 OpenMPI/3.1.4 
ml ORCA/4.2.1 

$EBROOTORCA/orca inputfile.inp

Make sure that the value to “-n” above matches the “nprocs” value in the input file.

Submit with 

sbatch <submitfile.sh>

Additional info

More information can be found on