Haddon's POAV2 vs POAV theory for non-planar molecules

In this note, we give a self-contained presentation of the POAV2 theory developed by Haddon to study the alignment of π-orbitals along a non-planar molecule. The classical POAV theory is purely geometric instead of the POAV2 which includes more physics in the computations. We compare the results obtained from the POAV2 and POAV theory. We prove that the difference between the two quantities is in most of the cases negligible. As a consequence, the POAV theory is sufficient for most of the purposes concerning the description of the local π-system of a molecule.