One cannot understand ... the universality of the laws of nature, the relationship of things, without an understanding of mathematics. There is no other way to do it." - Richard Feynman

See the NBO 5.0 website and associated order link for NBO5-level programs that interface with current or older NBO6-incompatible ESS versions.

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NBO Product Offerings

NBO 6.0 General Natural Bond Orbital Analysis program, for stand-alone GenNBO usage with any valid NBO archive .47 file, as well as for cooperative ESS/NBO interactions with any "NBO6-compatible" host electronic structure system (ESS). [Available as a binary executable (.exe) program for linux/mac/unix or PC-Windows platforms, or in source fortran code for compilation/linking on other platforms.]

Firefly NBO password Required password to activate NBO options in the Firefly (PC-GAMESS) program.

NBOView 2.0 NBO orbital viewer, to display profile (1D), contour (2D), and rendered surface plots (3D) of localized (NAO, NHO, NBO), semi-localized (NLMO), and delocalized (MO) orbitals (or pre-orthogonal counterparts). NBOView 2.0 features increased storage and full dimensional (basis/atoms) and angular (s/p/d/f/g) compatibility with NBO 6.0. [Available only as a binary executable (.exe) for PC-Windows.]

NBOPro 6.0 All-inclusive NBO6-level utility program for I/O-free integrated management of computational projects from initial molecular model to final chemical descriptors. NBOPro is composed of four interacting program modules:
  (1) NBOModel molecular design editor;
  (2) NBORun (GenNBO6-level) analysis;
  (3) NBOView 2.0 orbital viewer;
  (4) NBOSearch (NBO6-level) interactive data miner.
[Full GenNBO6 and NBOView 2.0 capability included; available only as a binary executable (.exe) for PC-Windows systems. Note that this program may not display properly on PCs with installed Windows-CJK (Chinese-Japanese-Korean) operating system and character sets; see FAQ 31.]

(The previous NBO5-level NBOPro v. 1.0 program has been moved to the NBO5 website order form. Upon request to, previous purchasers of the legacy NBO5-level program may upgrade to current NBOPro 6.0 at no cost.)

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