Given a set of calculated singlet states (but the same approach can be extended for states of other multiplicities), each state is evaluated singularly and the final score of the method/functional is given by their sum (Figure ). The score of a single state is in the range of 0-1 and it is the combination of a partial score due to the similarity of the character, the energy differences, and the brightness differences, with respect to the more accurate method, assigned in the following way: