I am interested in knowing what the physical interpretation of NBO analysis is. I have done NBO calculation for some molecules using GAMESS code. How can NBO explain the stability of molecules?
NBO analysis provide the electronic density distribution on atoms and bonds. By comparing a set of molecules you can for instance see the donor or acceptor effect of the substituent. I think I don't really understand what you mean by "How can NBO explain the stability of molecules?". COuld you elaborate?
An NBO analysis describes the Lewislike molecular bonding pattern of electron pairs (or of individual electrons in the open-shell case) in the optimally compact form of the molecule. More precisely, NBOs are orthonormal sets of localized “maximum occupancy” orbitals whose leading N/2 members (or N members in the open-shell case) give the most accurate possible Lewis-like description of the total N-electron density. The Lewis-type NBOs determine the localized natural Lewis structure (NLS) representation of the wave function, while the remaining “non-Lewis-type” NBOs complete the span of the basis and describe the residual “delocalization effects” (i.e., departures from a single localized Lewis structure) by second order pertubation energies. NBO analysis is a helpful tool for understanding the delocalization of the electron density, hyperconjugation effects and is very useful to to measure an intermolecular or intramolecular interaction!
@Renyer Costa
"NBO analysis is a helpful tool for understanding the delocalization of the electron density, hyperconjugation effects and is very useful to measure an intermolecular or intramolecular interaction!"
could you explain more? or give details reference for that.
Thanks in advance.
@Radwan Alnajjar by a NBO calculation you can understanding the delocalization of the electron density from the occupied Lewis-type (donor) NBOs to properly unoccupied non-Lewis-type (acceptor) NBOs [43–47] within the molecule.
This analysis uses the second-order perturbation energies 𝐸(2) [donor (𝑖) → acceptor (𝑗)] that involve the most important delocalization instances, when you submit a nbo calculation in the .log output (in gaussian software for exemple) its given the second order pertubation energies, and by the transtions energies you can estimate the hyperconjugative interactions, intramolecular interactions and in the case of a dimer for exemple you can estimate the energy of the intermolecular interaction
@Radwan Alnajjar http://nbo6.chem.wisc.edu/tutorial.html look this link , in the period that i was studying NBOs i have been read a lot this site!
The Natural Bond Orbital analysis explains the most important orbital interactions in order to clarify general structural features.
In the log file i found a lot of bonds donor-acceptor, i don't know which one i should take.
Dear Asheesh Kumar
Has there any maximum upper limit in the value of E2 ? because in my case i m getting an abnormally high value like 332 kCal/mol. Is this considerable?
Can anyone please suggest me what is the reliable value of second order perturbation energy of considering delocalization of electrons? Is there any maxima or minima on the energy value?
NBO analysis can offer more information for the hyperconjugation effect and the donor-acceptor interactions
- Badges
- Science topic
- Similar topics
- Correction