I have a molecule bearing a quaternary ammonium and I optimized it using M062X (also Hartree-Fock) using basis sets 6-31G(d,p) and 6-31G+(d,p) respectively. After optimization, I expect that the charge on the quaternary nitrogen would be positive. However, it's negative.
I ran the Gaussian to compute NBO charges and analysed the checkpoint files as well as log files. Nowhere could I see a positive charge on any nitrogen atom.
Why is this happening? And how can I obtain a positive charge on the quaternary nitrogen?
Many thanks in advance.