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Natural Bond Order (NBO) is restricted software.

Usage of this software is restricted to Laboratory for Molecular Simulation (LMS) subscribers. If you believe you are eligible to use NBO on our clusters, please email the HPRC Help Desk with the request and justification.


The Natural Bond Orbital (NBO) program is a discovery tool for chemical insights from complex wavefunctions.


Those who have been approved for access will be able to run NBO as detailed in the sections below.

NBO 6 and 7 are integrated into the Gaussian installs on the HPRC systems. You only need to include the correct NBO keywords: Gaussian NBO6/7

To run NBO standalone or with another quantum code, please visit:


NBO modules have been created to assist setup up the environment.

Find the versions of NBO installed:

mla nbo

Load the module. Replace NBOVersion with the version of NBO you wish to use.


Loading the NBO module will set the NBO_HOME variable to the base directory of the NBO install and add the $NBO_HOME/bin directory to your PATH.

Example, to run NBO 7 with ORCA 5, you will need to load the modules for ORCA and NBO and set the following variables in your job file:

# unload any modules to start with a clean environment
ml purge
# load modules necessary for ORCA
ml GCC/10.3.0 OpenMPI/4.1.1 ORCA/5.0.2-shared
#  load the NBO module
ml NBO/7

#  set the variables needed for ORCA to find the NBO7 executables
export GENEXE=$NBO_HOME/bin/gennbo.i4.exe
export NBOEXE=$NBO_HOME/bin/nbo7.i4.exe

#  orca run line here

Frequently Asked Questions

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