This page is about the software package ORCA. For the cluster, see 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.
If you wish to use pre-built ORCA executables:
- You have to register at https://orcaforum.kofo.mpg.de/
- You will receive a first email to verify the email address and activate the account. Follow the instructions in that email.
- Once the registration is complete you will get a second email stating that the "registration for ORCA download and usage has been completed".
- 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/22.214.171.124.
See Using modules for general guidance.
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:
#!/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/126.96.36.199 $EBROOTORCA/orca benzene.inp
Example of the input 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 *
- To make sure that the program runs efficiently and makes use of all the resources or the cores asked for in your job script, please add this line
%pal nprocs <ncores> endto your input file as shown in the above example. Replace
<ncores>by the number of cores you used in your script.
Message Passing Interface