nwchem OverviewAccording to the NWChem website: "NWChem aims to provide its users with computational chemistry tools that are scalable both in their ability to treat large scientific computational chemistry problems efficiently, and in their use of available parallel computing resources from high-performance parallel supercomputers to conventional workstation clusters."
module load nwchemIt 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:
start h2o 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 end basis H library 6-31g O library 6-31g end task scfTo launch NWChem, 2 ranks per node are required, so a simple aprun line would be:
$ aprun -n2 -N2 nwchem [input filename]
CompilingThe 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/