Natural Bond Orbital Analysis

The analysis of natural bond orbitals (NBOs) has shown to be a useful tool that makes it easier to interpret electronic structure calculations in a way that makes chemical sense. NBO analysis substitutes a set of metastable localized bonding orbitals and lone pairs for the standard molecular orbitals of a delocalized domain. The analysis is "natural" since it just relies on the density matrix generated from the computations of the underlying electrical structure. This absence of artificial criteria makes conclusions more reliable and based on physics, while also providing chemical insights into bonding and reactivity.

Fig 1. The NBO charge of the anthracene in different solvents. (Salami N, et al. 2021)

Alfa Chemistry offers professional NBO analysis services to help clients solve the various application problems they encounter in the field of wave function research. Based on the idea of orbital interactions, NBO analysis enables the interpretation of numerous chemical phenomena like reactivity, stereoselectivity, basicity, and intra- and intermolecular energy barriers. It can also shed light on fascinating chemical features of bonding.

NBO Method

NBO analysis involves converting non-orthogonal atomic orbitals (AO) to "natural" atomic orbitals (NAO), hybrid orbitals (NHO), and bonded orbitals (NBO) by sequentially converting the complete and orthogonal sets. NBO analysis is based on the optimal conversion of a given wave function into a local form corresponding to the single-center ("lone pair") and double-center ("bond") elements of the chemist's Lewis structure diagram. These local basis sets use the fewest occupied orbitals to most quickly convergently characterize the electron density and other features. Most crucially, from the perspective of a chemist, an orbital map that is as close as feasible to the standard "textbook" Lewis structure of the molecule is provided by NBO analysis.

On a more technical level, the NBO localization protocol divides the NBO into core, bond-forming, anti-bond-forming and "Rydberg" (residual) orbitals. The core and bond-forming orbitals describe the strictly localized Lewis structure of the molecule. The sequence passes through various local basis sets in the following order: AO → NAO → NHOs → NBOs → NLMOs → CMOs.

Fig 2. Natural bond orbital (NBO) analysis of the DFT+DMFT Green's function for MbO₂. (Weber C, et al. 2014)

Our Service

Alfa Chemistry uses an updated version of the NBO program, NBO 5.0, which is integrated in the Gaussian 09W package and uses the CAM-B3LYP/6-311G(d,p) method. the results of the NBO analysis are given according to the standard orientation of the system given at the beginning of the Gaussian output file.

Examples of properties we can calculate on the basis of NBO include:

• Dipoles, polarizability, and atomic charges.
• Bonding-anti-bonding orbital interactions.
• Resonance structures (second-order perturbation theory).
• Order of bonds.
• Energy decomposition.
• Chemical shifts, J-coupling.
• Stereo analysis.
• Canonical MO analysis.

Our NBO analysis services significantly reduce costs, facilitate further experimentation, and accelerate the drug design process for our global customers. Our personalized, full-service approach will meet your innovative learning needs. If you are interested in our services, please feel free to contact us. We would be happy to work with you and see you succeed!

References

• Salami N, et al. (2021). "Electronic Structure of Solids and Molecules." Interface Science and Technology. 32: 325-373.
• Weber C, et al. (2014). "Renormalization of Myoglobin-Ligand Binding Energetics by Quantum Many-Body Effects." IProceedings of the National Academy of Sciences. 111(16): 5790-5795.