Mr. Poutás,

The NBO analysis is completely reliable. We have tested it on over 300 molecules (organics and inorganics) making parallel with other methods suchh as for example CAS or full potential ones. Despite the methods are different as methodology and the quantities can not be compared directly, the conclusions are identical.

Hello, NBO analysis is a very useful technique for getting information about charge densities over bonding and antibonding regions of molecules, about hydrogen bonding, bond orders,...

http://repositorio.uchile.cl/bitstream/handle/2250/119245/Mera_Adasme_Raul.pdf?sequence=1

I think NBO analysis is a powerful tool to describe the electronic state of a molecule. However, it is necessary to pay close attention to interpret intermolecular and intramolecular weak interactions (mainly dispersion forces). In other words, I think that it is necessary to pay attention to chemical bonds where electronic correlation is extremely effective.

To begin with, the NBO algorithm is not unique. We tried to find NBOs for several similar systems (complexes of B12N12 with HX, X=Cl,Br,I) and found that with default thresholds for the NBO program we got different orbitals (e.g. different number of lone-pair orbitals on nitrogen). We had to switch to a lower, nondefault threshold to prevent this behavior. Now, in our case we will be able to detect the problem quite easily (number of LPs different from expected 12), but in other cases it may be not so straightforward. Additionally, we have found the the second-order energies from NBO could possibly show trends, but they do not correlate well with e.g. total interaction energies. Here is the DOI of our paper Article Structure and Energetics of Complexes of B 12 N 12 with Hydr...