Construction of molecular orbital energy level diagrams by the method of progressive interactions of atomic orbitals
A method of building up molecular orbital systems by different routes is suggested so that in each route, atomic orbitals are added successively, one at a time, until the molecule of interest is complete. In general the molecular energy levels of a system after addition of an atomic orbital alternate with those before. This property is used to arrive at a diagrammatic representation of the molecular orbital energy levels of a molecule without having to specify values for the parameters involved. This method will apply to any variational problem where the approximate eigenfunction is expressed as a linear combination of other functions and the Hamiltonian remains unchanged when the basis set is increased by one.