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"It is nice to know that the computer understands the problem, but I would
like to understand it too."
- Eugene Wigner |
NBO Intro Slideshow
What Are NBOs?
NBO Keywords/Output
NBO Tutorials
What's New in NBO 7?
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The Natural Bond Orbital (NBO) program NBO 7.0
is a discovery tool for chemical insights from
complex wavefunctions. NBO 7.0 is the current
version of the broad suite
of 'natural' algorithms for optimally expressing numerical solutions of
Schrödinger's wave equation in the chemically intuitive
language of Lewis-like bonding patterns and associated resonance-type
'donor-acceptor' interactions.
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Through their close association with elementary Lewis structure
diagrams, NBOs provide a direct link to familiar valency
and bonding concepts. Unlike the delocalized MOs
(whose sprawling forms vary bewilderingly even between closely
related systems)
or unitarily-equivalent LMOs (whose occupancy degeneracies
persist for any preferred
"localizing" criterion), the NBOs have unique occupancies
and spatial forms that are highly conserved
and transferable from one molecular environment
to another.
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NBOs are local eigen-properties of the input wavefunction,
the intrinsic realizations of orbital-type bonding concepts
as originally envisioned by Pauling, Mulliken,
and Coulson. Unlike methods based on derivatives
of charge density (a quasi-classical concept), NBO analysis exhibits
the unifying beauty of quantum phase-matching and
superposition principles
in all chemical phenomena.
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NBO provides mutually consistent and comprehensive
analysis tools, ensuring harmonious chemical
interpretations from one property to another. The program is
uniformly implemented in leading electronic
structure packages, providing an authoritative framework for
state-of-the-art professional discourse. Widespread acceptance
of the NBO paradigm is reflected in the burgeoning number
of published applications (currently, ca. 2000 per year).
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[Check here for latest
bugfix and update announcements]
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February 8, 2021:
New release NBO 7.0.10 (8-Feb-2021) is
now available for download by all licensed users. This
release includes a parallel implementation of NRT for
Linux and MacOS (see the PARALLEL.NRT file in
the nbo7 root directory for details) and bug fixes for
gfortran 6-10. By default, the NRT algorithm now cycles
to convergence (NRTCYC=0) and eliminates resonance forms
that do not contribute to the resonance hybrid for six
consecutive cycles (NRTCULL=6).
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May 21, 2020:
New release NBO 7.0.9 (21-May-2020) is
now available for download by all licensed NBO7
and NBOPro7@Jmol users. The update includes
fixes for NLMO and RNBO analyses, Th point-group
symmetry, new NRTPR keyword, and new
NBOMEM environment variable for dynamic memory allocation
for GenNBO G09NBO and G16NBO interface programs (making
source-code edits largely unnecessary for large systems
that exceed default memory limits of the compiled
binary program).
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February 21, 2020:
The e-order
form for NBO 7.0 products has been revised
to include a link to the current License Agreement. In addition,
the ordering process for a Site License now requires
identification and title of the institutional officer
with appropriate signatory authority, as well as the "Responsible
Individual" (if different from the "Authorized Company or
Institutional Signatory") who directly receives the downloaded
program and administers its usage on site resources.
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February 17, 2020:
The e-order
form for products from the former NBO 6.0
website (decommissioned in November 2018) is being de-activated
as of today. However, the NBO6
download repository will remain accessible to licensed
users until March 1, 2020, after which all services to pre-NBO7
products will cease.
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February 11, 2020:
New release NBO 7.0.8 (11-Feb-2020) is
now available for download by all licensed NBO7
and NBOPro7@Jmol users.
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November 4, 2019:
The online NBOrXiv (.47 file repository)
for RUN applications in NBOPro7@Jmol
has been restored (after the security-mandated
URL change that broke communications in August).
Thanks to Zhi Yuan Foo for assistance, and
apologies to users who were affected by
temporary NBOrXiv inaccessibility.
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September 9, 2019:
New release NBO 7.0.7 (now available for
download by all licensed NBO7 users)
corrects a problem
in the initial G16 Rev. C.01 implementation of NEDA
(PC-windows G16W/NBO7 only)
and introduces the new NRTLONG keyword, which initiates
a more thorough NRT search for 3c/4e long-bonding
structures (all OS options).
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July 24, 2019:
NEDA for Gaussian (G16 Rev. C.01 or later):
Recently released
G16 Rev. C.01 includes improved interactive
functionality with NBO 7.0.5, including a new full-featured
implementation of Natural Energy Decomposition Analysis
(NEDA) that
is now available for download by all licensed NBO7
users.
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July 14-19, 2019: Bremen, Germany
"Tools for Chemical Bonding" Workshop,
sponsored by the European Crystallographic Association
and hosted by Prof. Simon Grabowsky of
the University of Bremen,
will feature NBO developers Clark Landis and Eric Glendening
in a presentation of "Discovering Chemistry
with NBO7" on Monday, July 15.
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June 7, 2019:
NBO7: New Vistas in Localized and Delocalized Chemical Bonding:
Journal article (DOI: 10.1002/JCC.25873)
describing new and improved features of NBO 7.0
is now available on the
Journal of Computational Chemistry
website.
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January 2, 2019:
New release NBO 7.0.2
that cures the PC-Windows issue of 11/19/2018 is
now available for download by all licensed NBO7
and NBOPro7@Jmol users.
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December 18, 2018:
Early Download Problem for NBOPro7@Jmol:
In the initial download package for NBOPro7@Jmol,
the .zip file failed to include the "unix2dos"
utility that is needed for RUN, VIEW, and SEARCH
modules. All NBOPro7@Jmol license holders should obtain
a fresh download package with the download code
provided at time of purchase. Our apologies!
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December 5, 2018:
Early Download Problems: In early NBO7 purchases,
the email sent to license holders contained the wrong
link (the legacy NBO6 download link). The correct link
address for NBO7 downloads should end in "nbo7.cgi"
(not "nbo6.cgi"). Our apologies!
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November 20, 2018:
If you purchased NBO 6.0 in the last few
weeks before NBO 7.0 release
(specifically, in the period
October 15-November 15, 2018), you are eligible for
a 50% refund on the purchase price for immediate
upgrade to current NBO 7.0 (offer expires
December 15, 2018). Contact Cara Jenkins
(tcinbo@chem.wisc.edu) with your NBO7 license information
to request the refund.
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November 19, 2018:
Temporarily, NBO 7.0 for PC-Windows is being released
only in 32-bit binaries without functioning MEMORY
keyword for dynamic memory allocation. (The default
scratch memory is still 1Gb, equivalent to that of
the intended 64-bit implementation.)
Watch here for notification when the full-featured 64-bit
NBO 7.0 binary for PC-Windows
(equivalent to linux and MacOSX binaries) replaces the
temporary 32-bit version in the website distribution link,
at which time licensed purchasers of NBO 7.0 (PC-Windows)
can download the 64-bit program at their convenience.
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November 15, 2018: NBO7 ANNOUNCEMENT DAY
NBO 7.0 is announced!
Following years of program development
and cooperation with affiliated ESS providers,
leading members of the NBO Team
(Eric Glendening, Clark Landis, Frank Weinhold) unveiled
the new
nbo7.chem.wisc.edu
website and announced public
availability of the
NBO 7.0
program, as well as enhanced
NBOPro7@Jmol
program.
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Claisen rearrangement illustrated with Resonance NBOs (RNBOs),
the newest addition to the NBO-based orbital family
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