text: For the simplest AH molecular system, Walsh produced the first angular correlation diagram by plotting the ab initio orbital energy curves for the canonical molecular orbitals while changing the bond angle from 90° to 180°.  As the bond angle is distorted, the energy for each of the orbitals can be followed along the lines, allowing a quick approximation of molecular energy as a function of conformation. It is still unclear whether or not the Walsh ordinate considers nuclear repulsion, and this remains a topic of debate. A typical prediction result for water is a bond angle of 90°, which is not even close to the experimental derived value of 104°. At best the method is able to differentiate between a bent and linear molecule.
  This same concept can be applied to other species including non-hydride AB and BAC molecules, HAB and HAAH molecules, tetraatomic hydride molecules (AH), tetraatomic nonhydride molecules (AB), HAB molecules, acetaldehyde, pentaatomic molecules (CH3I), hexatomic molecules (ethylene), and benzene.