where, on the grounds of previous experience, the CBS contribution can be safely neglected. To further extend the applicability of composite approaches to larger molecules, an effective solution is provided by the so-called "geometry" scheme. This is based on the assumption that the additivity approximation can be directly applied to geometrical parameters and only requires geometry optimizations at several levels of theory. The different contributions are thus evaluated separately and then combined together. This approach will be used in the following sections to analyze the role of different geometries on the final evaluation of electronic energies (∆GEOM contribution).