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Overview

Q-Chem is a comprehensive ab initio quantum chemistry package. Its capabilities range from the highest performance DFT/HF calculations to high level post-HF correlation methods. Q-Chem tackles a wide range of problems in commercial, academic and government laboratories, including:

  • Molecular Structures
  • Chemical Reactions
  • Molecular Vibrations
  • Electronic Spectra
  • NMR Spectra
  • Solvation Effects

Usage

To use parallel Q-Chem, load the qchem module with the command (Use module load avail qchem to see what versions are available). 

$ module load qchem/5.3.2

See here for more information about modules.

Here is an example of running a Q-Chem input deck under the PBS queueing system. The jobscript is called qchem_job.sh and will run a job with input file.inp on 4 processor requiring 32Gb of memory, and 100Gb of scratch area for integrals and temporary files.

#!/bin/bash

#PBS -l ncpus=4
#PBS -l walltime=24:00:00
#PBS -l mem=16Gb
#PBS -l jobfs=20gb
#PBS -l wd

# Load module, always specify version number.
module load qchem/5.3.2

# Must include `#PBS -l storage=scratch/ab12+gdata/yz98` if the job
# needs access to `/scratch/ab12/` and `/g/data/yz98/`. Details on:
# https://opus.nci.org.au/display/Help/PBS+Directives+Explained

qchem -nt $PBS_NCPUS file.inp file.out

To submit the job to the PBS queueing system, issue the command

$ qsub qchem_job.sh

Q-Chem on Gadi is build with openmp only, so it can only run on one node with up to 48 CPUs in normal queue.