Product software implementation method result in ambiguity when questions arise in the execution of the implementation process. On the other hand methods can be used as a profession, meaning that the method should be taken strict and the usage of the method should be a profession, instead of a guiding principle. This view is very useful if the implementation process is very complex and is very dependent on exact and precise acting. Organizational and quality management will embrace this view, as a strict usage of any method results in more clarity on organizational level. Change management however might indicate that more flexibility in an
Extended Hückel method to be done. One usually does this by adjusting the orbitals in the new basis to the old ones by least squares method. As only valence electron wavefunctions are found by this method, one must fill the core electron functions by orthonormalizing the rest of the basis set with the calculated orbitals and then selecting the ones with less energy. This leads to the determination of more accurate structures and electronic properties, or in the case of ab initio methods, to somewhat faster convergence. The method was first used by Roald Hoffmann who developed, with Robert Burns Woodward, rules for