Q-Chem is a comprehensive ab initio quantum chemistry package for accurate predictions of molecular structures, reactivities, and vibrational, electronic and NMR spectra. The new release of Q-Chem 4.0 represents the state-of-the-art of methodology from the highest performance DFT/HF calculations to high level post-HF correlation methods:

• Dispersion-corrected and double hybrid DFT functionals
• Faster algorithms for DFT, HF and coupled-cluster calculations;
• Structures and vibrations of excited states with TD-DFT;
• Methods for mapping complicated potential energy surfaces;
• Efficient valence space models for strong correlation;
• More choices for excited states, solvation and charge-transfer;
• Effective Fragment Potential and QM/MM for large systems;
• Shared-memory for multicores and implementations for GPU's.

• Q-Chem 5.0 manual

• Module Name: qchem (see the modules page for more information)
• Q-Chem can use threads or MPI processes to parallelize. Different methods within Q-Chem can utilize one or both kinds of parallelization. See the section on Running Q-Chem in parallel for more information. OpenMP (threads) can utilize multiple cores on a node, but cannot run on multiple nodes.
• After you run 'module load qchem', a set of example input files is available in $QC/samples.
• Reference data in /fdb/qchem/

Create a batch input file (e.g. qchem.sh). For example:

#!/bin/bash
#SBATCH --job-name="QC"
#SBATCH --mail-type=BEGIN,END

module load qchem/4.3

cd /data/$USER/qchem

# copy the sample data to this directory
cp ${QC}/samples/bsse/frgm_mp2_h2o_h2o_h2o.in .

# run qchem
qchem -nt $SLURM_CPUS_PER_TASK  frgm_mp2_h2o_h2o_h2o.in   frgm_mp2_h2o_h2o_h2o.in.out

Submit this job using the Slurm sbatch command. e.g.

sbatch --cpus-per-task=16  --threads-per-core=1 --mem=20g qchem.sh

When the qchem module is loaded as part of a batch job, it sets the environment variable $QCLOCALSCR to '/lscratch/$SLURM_JOBID' . This directory is only created if you submit the job with --gres=lscratch:#. (see the User Guide section on using local disk.

#!/bin/bash
#SBATCH --job-name="QC"

module load qchem/4.3

cd /data/$USER/qchem

# copy the sample input file to this directory
cp  ${QC}/samples/sp/dft_b5050lyp_c4h6.in .

# run qchem
make-qchem-nodefile
export QCMACHINEFILE=`pwd`/qchem.$SLURM_JOBID.nodes
qchem -np $SLURM_NTASKS  dft_b5050lyp_c4h6.in   dft_b5050lyp_c4h6.in.out
rm $QCMACHINEFILE

Submit this job with:

biowulf% sbatch --ntasks=4 --ntasks-per-core=1  --gres=lscratch:100 qchem.bat

where:

make-qchem-nodefile	a script that writes a file containing a list of nodes to be used
$QCMACHINEFILE	environment variable used by Q-Chem to determine the nodes on which to run
-np $SLURM_NTASKS	tells Q-Chem to run $SLURM_NTASKS MPI processes
--ntasks=4	tells Slurm how many tasks (MPI processes) to run
--ntasks-per-core=1	tells Slurm to run only one task on each physical core (i.e. ignore hyperthreading). This is usually recommended for cpu-intensive parallel jobs.
--gres=lscratch:100	specifies that 100 GB of local scratch on the node should be allocated to this job. This parameter is required for all Qchem job submissions.