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Comparing an MO with the Corresponding NBO Using WebMO
Comparing an MO with the Corresponding NBO Using WebMO
Published: 2016/04/10
Channel: John Keller
Avogadro with Gaussian + NBO
Avogadro with Gaussian + NBO
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Visualizing Natural Bond Orbitals
Published: 2013/03/05
Channel: ccclabmit
Multiple NBOS With GaussView and WebMO
Multiple NBOS With GaussView and WebMO
Published: 2016/04/12
Channel: John Keller
Orbitals: Crash Course Chemistry #25
Orbitals: Crash Course Chemistry #25
Published: 2013/08/05
Channel: CrashCourse
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Jmol-NBO Visualization Helper
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Channel: Org Med Chem
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How to circulate your sexual energy with the Microcosmic Orbit - Taoist Meditation
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[3,3]-Sigmatropic Rearrangements - Intrinsic Bond Orbitals
[3,3]-Sigmatropic Rearrangements - Intrinsic Bond Orbitals
Published: 2017/03/29
Channel: ClickChemist
Orbitals, the Basics: Atomic Orbital Tutorial — probability, shapes, energy; Crash Chemistry Academy
Orbitals, the Basics: Atomic Orbital Tutorial — probability, shapes, energy; Crash Chemistry Academy
Published: 2011/08/01
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The Tetrazine Ligation - Intrinsic Bond Orbitals
The Tetrazine Ligation - Intrinsic Bond Orbitals
Published: 2017/02/28
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Frontier Molecular Orbital Theory (FMO Theory) & Gaussian |  | Part I
Frontier Molecular Orbital Theory (FMO Theory) & Gaussian | | Part I
Published: 2017/06/04
Channel: Transition State
ETS-NOCV: Advanced chemical bonding analysis
ETS-NOCV: Advanced chemical bonding analysis
Published: 2014/03/03
Channel: AmsterdamDensityFunctional
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NBO visualizer FAIL
Published: 2015/10/25
Channel: IaNiusha
Budwig Protocol in UNDER TWO MINUTES.
Budwig Protocol in UNDER TWO MINUTES.
Published: 2017/01/17
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Polymers - Crash Course Chemistry #45
Polymers - Crash Course Chemistry #45
Published: 2014/01/06
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Orbitals, the Basics: Atomic Orbital Tutorial — probability, shapes, energy; Crash Chemistry Academy
Orbitals, the Basics: Atomic Orbital Tutorial — probability, shapes, energy; Crash Chemistry Academy
Published: 2017/09/23
Channel: ELLENT
Jmol Viewer and display of NBOs in web browsers
Jmol Viewer and display of NBOs in web browsers
Published: 2012/11/18
Channel: Org Med Chem
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Interpreting Gaussian Results
Published: 2012/07/25
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Avogadro with Gaussian Tutorial MOs
Avogadro with Gaussian Tutorial MOs
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Channel: IaNiusha
The Electron: Crash Course Chemistry #5
The Electron: Crash Course Chemistry #5
Published: 2013/03/12
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The Electron Cloud Model explained + Animation & atomic Orbitals tutorial; Crash Chemistry Academy
The Electron Cloud Model explained + Animation & atomic Orbitals tutorial; Crash Chemistry Academy
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Channel: Crash Chemistry Academy
Localized Molecular Orbital Theory
Localized Molecular Orbital Theory
Published: 2012/06/05
Channel: Michael Evans
Organic Chemistry 1 - Introduction / Basic Overview
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Channel: The Organic Chemistry Tutor
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Resonance Made Easy! Finding the Most Stable Resonance Structure - Organic Chemistry
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Non-Conservativeness of Natural Orbital Systems by Slobodan Nedic
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Hydrocarbon Power! - Crash Course Chemistry #40
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Molecular Orbitals and Resonance
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Molecular Orbitals of Ethene
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Published: 2008/04/29
Channel: MIT OpenCourseWare
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WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
  (Redirected from Natural Bond Orbital)
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In quantum chemistry, a natural bond orbital or NBO is a calculated bonding orbital with maximum electron density. The NBOs are one of a sequence of natural localized orbital sets that include "natural atomic orbitals" (NAO), "natural hybrid orbitals" (NHO), "natural bonding orbitals" (NBO) and "natural (semi-)localized molecular orbitals" (NLMO). These natural localized sets are intermediate between basis atomic orbitals (AO) and molecular orbitals (MO):

Atomic orbital → NAO → NHO → NBO → NLMO → Molecular orbital

Natural (localized) orbitals are used in computational chemistry to calculate the distribution of electron density in atoms and in bonds between atoms. They have the "maximum-occupancy character" in localized 1-center and 2-center regions of the molecule. Natural bond orbitals (NBOs) include the highest possible percentage of the electron density, ideally close to 2.000, providing the most accurate possible “natural Lewis structure” of ψ. A high percentage of electron density (denoted %-ρL), often found to be >99% for common organic molecules, correspond with an accurate natural Lewis structure.

The concept of natural orbitals was first introduced by Per-Olov Löwdin in 1955, to describe the unique set of orthonormal 1-electron functions that are intrinsic to the N-electron wavefunction.[1]

Theory[edit]

Each bonding NBO σAB (the donor) can be written in terms of two directed valence hybrids (NHOs) hA, hB on atoms A and B, with corresponding polarization coefficients cA, cB:

σAB = cA hΑ + cB hB

The bonds vary smoothly from covalent (cA = cB) to ionic (cA >> cB) limit.

Each valence bonding NBO σ must be paired with a corresponding valence antibonding NBO σ* (the acceptor) to complete the span of the valence space:

σAB* = cA hΑcB hB

The bonding NBOs are of the "Lewis orbital"-type (occupation numbers near 2); antibonding NBOs are of the "non-Lewis orbital"-type (occupation numbers near 0). In an idealized Lewis structure, full Lewis orbitals (two electrons) are complemented by formally empty non-Lewis orbitals. Weak occupancies of the valence antibonds signal irreducible departures from an idealized localized Lewis structure, which means true "delocalization effects".[1]

Lewis structures[edit]

With a computer program that can calculate NBOs, optimal Lewis structures can be found. An optimal Lewis structure can be defined as that one with the maximum amount of electronic charge in Lewis orbitals (Lewis charge). A low amount of electronic charge in Lewis orbitals indicates strong effects of electron delocalization.

In resonance structures, major and minor contributing structures may exist. For amides, for example, NBO calculations show that the structure with a carbonyl double bond is the dominant Lewis structure. However, in NBO calculations, "covalent-ionic resonance" is not needed due to the inclusion of bond-polarity effects in the resonance structures.[2] This is similar to other modern valence bond theory methods.

See also[edit]

References[edit]

  1. ^ a b Weinhold, Frank; Landis, Clark R. (2001). "Natural Bond Orbitals and Extensions of Localized Bonding Concepts" (PDF). Chemistry Education Research and Practice. 2 (2): 91–104. doi:10.1039/B1RP90011K. 
  2. ^ Weinhold, Frank; Landis, Clark R. (2012). Discovering Chemistry With Natural Bond Orbitals. New Jersey: John Wiley & Sons. pp. 132–133. ISBN 978-1-118-22916-3. 

External links[edit]

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