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. Once the registration is complete you will get an email stating that the "registration for ORCA download and usage has been completed".
   (This is the second email that you will receive.)
3. 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 s ubmission=== 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 benzen.inp

Example of the input file, benzene.inp:

File : benzen.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
*

Message Passing Interface