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ORCA

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General Description

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. To know more about this software, please check ORCA webpage.

Basic Usage

ORCA environment can be set with the following module command:

module load orca

Submitting a job to SGE

A serial job can be submitted with the script as:

#!/bin/bash

#$ -M netid@nd.edu       # Email address for job notification
#$ -m abe                # Send mail when job begins, ends and aborts
#$ -pe smp 1             # Specify parallel environment and legal core size
#$ -q long               # Specify queue
#$ -N job_name           # Specify job name

module load orca

echo "Job Started at:"
date

orca_exc=`which orca`

$orca_exc H2O2MA2.inp >& p1.out

echo "Job Ended at:"
date

A parallel job can be submitted on single/multiple node(s). To run on a single node:

#!/bin/bash

#$ -M netid@nd.edu       # Email address for job notification
#$ -m abe                # Send mail when job begins, ends and aborts
#$ -pe smp 8             # Specify parallel environment and legal core size
#$ -q long               # Specify queue
#$ -N job_name           # Specify job name

module load orca

echo "Job Started at:"
date

orca_exc=`which orca`

$orca_exc H2O2MA2.inp >& p8.out

echo "Job Ended at:"
date

To run on multiple nodes:

#!/bin/bash

#$ -M netid@nd.edu       # Email address for job notification
#$ -m abe                # Send mail when job begins, ends and aborts
#$ -pe mpi-12 24         # Specify parallel environment and legal core size
#$ -q long               # Specify queue
#$ -N job_name           # Specify job name

module load orca

echo "Job Started at:"
date

orca_exc=`which orca`

$orca_exc H2O2MA2.inp >& p24.out

echo "Job Ended at:"
date

Notes on parallel runs:

  • Orca is pre-compiled and currently it supports only OpenMPI. For parallel runs, you don't use 'mpirun' or 'mpiexec' as they are intrincically set within the build.
  • As of Orca version 3.0.x following modules are parallelized - SCF, SCFGRAD, CASSCF/NEVPT2, MDCI (Coupled-Cluster), CPSCF, CIS/TDDFT, MP2 and RI-MP2, (including gradient), EPRNMR, SOC, ROCIS, PC, MRCI, Numerical Gradients and Frequencies
  • For parallel runs, you must use the full path to the executable (this is taken care of the above sample scripts).
  • Typically ORCA scales well on up to 8 CPUs. For example, coupled cluster calculations usually scale well up to at least 8 processors but probably it is also worthwhile to try 16. Please do the scaling test on your applications and accordingly set the CPUs number.
  • For parallel runs, please use the following directive, specifying the number of CPUs to be used, on the top of your input file.
! PAL4  # everything from PAL2 to PAL8 is recognized

or

%pal 
 nprocs 4 # any positive integer number 
end

Tutorials

A few examples on a water dimer (SCF calculation) running as serial and parallel are available at /afs/crc.nd.edu/x86_64_linux/orca/Tutorials. Beginners are welcome to copy these examples to their own space and can practice. To run please follow README file.

Further Information

See the official website: ORCA