ORCA

General

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.

• Project site: https://orcaforum.kofo.mpg.de/app.php/portal

• Installation Manual: https://www.orcasoftware.de/tutorials_orca/first_steps/install.html

Licensing

If you wish to use centrally installed prebuilt ORCA executables:

1. You have to register at https://orcaforum.kofo.mpg.de/
2. You will receive a first email to verify the email address and activate the account. Follow the instructions in that email.
3. Once the registration is complete, you will get a second email stating that the "registration for ORCA download and usage has been completed".
4. Contact us requesting access to ORCA with a copy of the second email at support@hpc.ucalgary.ca.

Note: You do not need to ask a permission from us, if you are willing to download ORCA and install it in your home directory on your own. You only need to contact us if you are planning on using the centrally installed ORCA using the module command.

ORCA on ARC

To see available versions of ORCA on ARC, use the module command:

$ module avail orca
----------------------- /global/software/Modules/4.6.0/modulefiles -----------------------
orca/5.0.3-shared  orca/5.0.3-static  

At the moment of writing there are two modules that provide the same version of ORCA, v5.0.3. The modules are based on the binary distributions provided by the developers, for shared and static builds of of the executable files.

For parallel runs orca needs an MPI library. On ARC it depends on the openmpi/4.1.1-gnu module.

Test case

ORCA input file, trimer.inp:

# Beryllium Hydroxo Cation Trimer 
%pal nprocs 48 end
! RHF TightSCF PModel
! opt

* xyz 3 1
BE    -0.8525564731   1.4385952336  -0.0568386129
BE    -0.8439106317  -1.4629929631  -0.0609922493
BE     1.6646301187  -0.0047356303  -0.0492110057
O     -1.4961121024   2.3487644892   1.2288561938
O     -1.3182244409  -2.4739274717   1.2229994716
O      2.7600572652  -0.0952297793  -1.3493767865
O     -1.3120368956   2.4299969307  -1.3624682759
O     -1.4647109135  -2.3581289822  -1.3693992968
O      2.7677255286   0.0905655941   1.2430198205
H     -1.8119923339   1.9892271297   2.0517208639
H     -0.8530364757  -2.5680042291   2.0481697576
H      3.5593293692   0.4144864646  -1.4503014673
H     -2.1528769106   2.8657164542  -1.4716703585
H     -1.4216692255  -3.3043858812  -1.4768305047
H      2.6169144032  -0.5871082502  -2.1516801328
H     -0.8074101333   2.5517677785  -2.1603597618
H     -1.8167790717  -1.9829473649  -2.1702654859
H      3.5918724943  -0.3831545116   1.3144677218
H     -1.5005192072   3.2996000227   1.2972549220
H     -2.1403067026  -2.9521565768   1.2875415691
H      2.6106062441   0.5414374312   2.0666175658
O      0.7464193743  -1.3117753249  -0.0488528410
O      0.7384467702   1.2969248953  -0.0443089227
O     -1.5167658775  -0.0143091197  -0.0541930119
H      1.2233662484  -2.1319290025  -0.0335893416
H      1.2100703374   2.1200534530  -0.0251688186
H     -2.4654622393  -0.0174143863  -0.0404919530
*

In this example, the number of MPI processes is set to 48, which is specific to the cpu2021 and cpu2021-bf24 partitions on ARC. Please, do not forget to change that number according to the partition you are going to run it on.

The job script for the trimer example, trimer.slurm:

#! /bin/bash
# ===========================================================================
#SBATCH --job-name=orca_test
#SBATCH --nodes=1
#SBATCH --ntasks=48
#SBATCH --cpus-per-task=1
#SBATCH --mem=64GB
#SBATCH --time=0-5:00:00
#SBATCH --partition=cpu2021-bf24

# ===========================================================================
module load openmpi/4.1.1-gnu
module load orca/5.0.4-static

ORCA=`which orca`

$ORCA trimer.inp
# ===========================================================================

NOTE, that for parallel runs ORCA insists on being started using full absolute path. Not just with the orca commmad, but using /global/software/orca/5.0.4-static/orca full name.

This is why the line

ORCA=`which orca`

is required.

Links

ARC Software pages