A natural bond orbital (NBO) refers to a concept in the field of quantum chemistry that is used to describe the nature of chemical bonding within a molecule. It is a mathematical construct that presents a localized representation of the electron density distribution in a molecule.
In more technical terms, NBOs are obtained by a process called canonical molecular orbital analysis, which involves orthogonalizing the molecular orbitals and expressing them as a linear combination of basis functions. The NBOs resulting from this analysis are typically occupied by one or two electrons, and they represent the most stable, chemically meaningful orbitals in a molecule.
NBOs have proven to be very useful in the interpretation and understanding of chemical bonding, as they provide insight into the electron density distribution and the nature of the bonding interactions within a molecule. They allow for the identification and characterization of different types of chemical bonds such as sigma bonds, pi bonds, lone pairs, and charge transfer interactions.
Moreover, NBOs enable the quantification of the delocalization and hyperconjugation effects, which influence the stability and reactivity of molecules. By analyzing the energy levels and populations of the NBOs, it is possible to determine the electron density in specific regions of a molecule, providing valuable information about its chemical behavior.
In summary, a natural bond orbital is a localized orbital that represents the electron density distribution and chemical bonding within a molecule. It serves as a powerful tool for understanding the nature of chemical bonds, electron delocalization, and reactivity patterns.
