ORCA

This page is about the software package ORCA. For the cluster, see Orca.

Introduction

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.

Licensing

If you wish to use pre-built 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 registration email mentioned above.

Using the software

To see what versions of ORCA are currently available, type module spider orca. For detailed information about a specific version, including what other modules must be loaded first, use the module's full name. For example, module spider orca/4.0.1.2.

See Using modules for general guidance.

Job submission

For a general discussion about submitting jobs, see Running jobs.

NOTE: If you run into MPI errors with some of the ORCA executables, you can try to define the following variables:

export OMPI_MCA_mtl='^mxm'
export OMPI_MCA_pml='^yalla'

The following is a job script to run ORCA using MPI:

File : run_orca.sh

#!/bin/bash
#SBATCH --ntasks=8                 # cpus, the nprocs defined in the input file
#SBATCH --mem-per-cpu=3G           # memory per cpu
#SBATCH --time=00-03:00            # time (DD-HH:MM)
#SBATCH --output=benzene.log       # output .log file

module load openmpi/2.0.2
module load orca/4.0.1.2
$EBROOTORCA/orca benzene.inp

Example of the input file, benzene.inp:

File : benzene.inp

# Benzene RHF Opt Calculation
%pal nprocs 8 end
! RHF TightSCF PModel
! opt

* xyz 0 1
     C    0.000000000000     1.398696930758     0.000000000000
     C    0.000000000000    -1.398696930758     0.000000000000
     C    1.211265339156     0.699329968382     0.000000000000
     C    1.211265339156    -0.699329968382     0.000000000000
     C   -1.211265339156     0.699329968382     0.000000000000
     C   -1.211265339156    -0.699329968382     0.000000000000
     H    0.000000000000     2.491406946734     0.000000000000
     H    0.000000000000    -2.491406946734     0.000000000000
     H    2.157597486829     1.245660462400     0.000000000000
     H    2.157597486829    -1.245660462400     0.000000000000
     H   -2.157597486829     1.245660462400     0.000000000000
     H   -2.157597486829    -1.245660462400     0.000000000000
*

Notes

• To make sure that the program make use of all the resources or the cores asked for in your job script, please add this line %pal nprocs <ncores> end to your input file as shown in the above example. Replace <ncores> by the number of cores you used in your slurm script.

Message Passing Interface