"The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them." - Wm. L. Bragg

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News Archive FAQ Forum Featured apps NBO team contact us

Send us (tcinbo@chem.wisc.edu) a blurb about your latest, greatest NBO-based application -- including reference(s), illustrative "Graphic Abstract," brief synopsis, and "more" link -- for possible inclusion in this listing.

Venerable "18e Rule" Re-derived

C. R. Landis and F. Weinhold, "18-Electron Rule and the 3c/4e Hyperbonding Saturation Limit," J. Comp. Chem. (2015), DOI: 10.1002/jcc.24001

In a special issue of J. Comp. Chem. memorializing Prof. P. v.R. Schleyer, researchers from the University of Wisconsin have shown that the empirical 18-electron rule of transition metal chemistry corresponds to an intrinsic saturation limit for the 3c/4e hyperbonding interactions that are a ubiquitous feature of D-block aggregation phenomena. Such a "rule" therefore requires no "p-orbital participation," "d2sp3 hybridization," "valence shell expansion," or other p-type intrusions into the Aufbau orbital filling sequence... more

Taming Peroxide Instabilities with Hyperconjugation

[G. Passos Gomes, V. A. Vil', A. Terent'ev, and I. Alabugin, "Stereoelectronic source of the anomalous stability of bis-peroxides," Chem. Sci. (2015), DOI: 1039/C5SC02402A]

As reported in Chemistry World (22 October 2015), a research team led by Prof. I. V. Alabugin of Florida State University has employed NBO techniques to unravel the paradoxical instabilities of peroxide species... more

Linear-scaling NAO/NHO/NBO construction

[T. Ohwaki, M. Otari, and T. Ozaki, "A method of orbital analysis for large-scale first-principles simulations," J. Chem. Phys. 140, 244105 (2014)]

Researchers from the Nissan Resarch Center, National Institute of Advanced Industrial Science and Technology (AIST), and Japan Advanced Institute of Science and Technology (JAIST) have developed an efficient method for calculating NBOs of a localized reaction region in the framework of DFT-based large-scale O(N) first-principles MD simulations. The method was demonstrated in a variety of test models [272-atom molecular electrolyte cluster, 217-atom diamond cell, 147-atom cubeoctahedral Pt cluster, and 192-atom 4x4 Pt(111) slab] and employed to study reactive ligand exchanges in a 2176-atom simulation of propylene carbonate/LiBF4 bulk liquid electrolyte, of importance in development of high-performance ion batteries... more

Clashing Hydrogens: Repulsive or Attractive?

[F. Weinhold, P. v.R. Schleyer, and W. C. McKee, J. Comp. Chem. 35, 1499-1508 (2014)]

Researchers from the University of Wisconsin and University of Georgia report on page 1499 (DOI: 10.1002/jcc.23654) that quantitative NBO-based evaluations of steric (left) and hyperconjugative (right) interactions in the illustrative model cis-2-butene demonstrate the dominance of steric repulsions over attractive 'H-H bonding' in biphenyl and related species, contrary to inferences based on QTAIM analysis... more

NBO Description of an unusual 4-center 2-electron bond

[A. Nova, H.-W. Suh, T. J. Schmeier, L. M. Guard, O. Eisenstein, N. Hazari, and F. Maseras, "An unusual example of hypervalent silicon: A five-coordinate silyl group bridging two palladium or nickel centers through a nonsymmetrical four-center two-electron bond," Angew. Chem. Int. Ed. 53, 1103 (2014)]

Researchers from the University of Oslo, ICIQ, Université Montpellier 2 and Yale University have used NBO to describe the electronic structure of a five-coordinate silyl group bridging two palladium or nickel centers. Crystallographic characterization revealed a rare square-pyramidal geometry at Si and an unusual asymmetric M2Si2 core (M=Pd or Ni) held by two pincer PsiP ligands. DFT calculations showed that the unusual structure of the core is not imposed by the PSiP ligands. NBO analysis showed that an asymmetric four-center two-electron (4c/2e) bond stabilizes the hypervalent Si atoms in the M2Si2 core... more

Java-based utility programs to simplify NBO input preparation and visualization

Marcel Patek of marcelpatek.com (Tucson, AZ) is providing a series of Java-based PC-windows utilities (Gennbo Helper, Jmol-NBO Visualization Helper,...) to simplify preparation of $NBO input files and exhibit Jmol-based orbital imagery. Each utility is provided with an introductory video to demonstrate usage and capabilities of the program... more

Grid-based NBOs in ONETEP linear-scaling DFT Applications to protein-protein interactions

[L. P. Lee, D. J. Cole, M. C. Payne, and C.-K. Skylaris, "Natural Bond Orbital Analysis in Linear-Scaling Density Functional Theory Calculations: application to a protein-protein interface" (J. Comp. Chem. 34, 429 (2013)]

Members of the ONETEP (Order-N Electronic Total Energy Package) Developers Group of Cambridge U. (UK) and U. Southhampton (UK) have succeeded in extracting NBOs from large-scale (>8000 atoms) DFT simulations of the entire protein-protein complex between human RAD51 and BRCA2, thereby elucidating the mechanism of interaction in terms of the location and strength of "energetic hotspots" that contribute the bulk of the binding energy. The NBO results exhibit the hyperconjugative interactions between non-bonding electron pairs and antibonding pi* NBOs that provide a hitherto unknown stabilization mechanism for the protein conformation that leads to maximum interaction between the energetic hotspots... more

Plane-wave NBOs in Periodic Systems

[B. D. Dunnington and J. R. Schmidt, J. Chem. Theor. Comp. 8, 1902 (2012)]

Prof. J. R. Schmidt and graduate student Benjamin Dunnington (UW-Madison) have developed an extension of the Natural Bond Orbital (NBO) orbital localization procedure to solid-state periodic systems and surface models. The resulting NBO analysis yields a chemically-intuitive "general chemistry" Lewis-like picture of bonding between catalysts / adsorbate in terms of localized orbitals... more

NBO-based "Natural Orbital Fukui Function"

[P. Zhou, P. W. Ayers, S. Liu, and T. Li, Phys. Chem. Chem. Phys 14, 9890 (2012)]

Researchers from U. Kentucky, McMaster University, and U. North Carolina have proposed a new condensed form of the Fukui function, the natural orbital Fukui function (NOFF), derived from natural bond orbital occupancy. It is defined as the change in natural bond orbital occupancy upon electronic perturbation (electron addition to, or depletion from, a molecular system). Applying NOFF to a series of cycloaddition reactions (e.g., [4 + 2] and [2 + 1] cycloadditions) illustrates the effectiveness of the concept in interpreting bond breakage and formation mechanisms.... more

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