module load nwchem
It is recommended to set the following environment variables on Titan when using NWChem.
$ export ARMCI_DMAPP_LOCK_ON_GET=1
$ export ARMCI_DMAPP_LOCK_ON_PUT=1
$ export APRUN_BALANCED_INJECTION=64
(The specific value to use will vary by problem and job size.)
This prevents a high network traffic situation that degrades the performance of all jobs on the system.
For more info see: https://www.olcf.ornl.gov/kb_articles/using-balanced-injection/
A sample input file for water could look like this:
title "Water in 6-31g basis set"
geometry units au
O 0.00000000 0.00000000 0.00000000
H 0.00000000 1.43042809 -1.10715266
H 0.00000000 -1.43042809 -1.10715266
H library 6-31g
O library 6-31g
To launch NWChem, 2 ranks per node are required, so a simple aprun line would be:
$ aprun -n2 -N2 nwchem [input filename]
The OLCF provides a version of NWChem. If additional builds are required, the package can be built in a user's home directory or in the project's /ccs/proj/ directory. Build instructions can be found on the Compiling NWChem page.