The electron density can be analyzed in a similar way to the orbitals. In most cases, a topological analysis of the density is used, which is a kind of a functional analysis approach. The most prominent ansatz here is the atoms-in-molecules (AIM) approach developed by Richard Bader. AIM delivers atomic basins, bond paths and many derived quantities (e.g., partial charges). It is rarely used for surface chemistry and thus has not been used in AS-ALD up to now. A simpler approach is visualizing charge-density differences. In this case, the electron density of a precursorsubstrate complex is taken, and the electron density from the separated precursor and substrate is subtracted. Thus, one derives the density changes induced by the bonding interaction. This approach is very common in surface science and has also been used in AS-ALD. Yet, it has the disadvantage that the resulting figures often do not allow a straightforward analysis regarding the most important interactions.