Currently used DFs show some major inaccuracies. One well-known issue is the gross underestimation of band gaps of semiconductors by GGA functionals which can be traced back to the delocalization error (called the self-interaction error for one-electron systems). Connected to the same underlying cause is the over-delocalization (GGAs) and over-localization (hybrid DFs) of electron densities. This can lead to errors in dissociation energies and especially reaction barriers but is mostly relevant for electron transfer phenomena. The second issue is the inadequate description of static correlation effects. This can be understood as the result of one Slater determinant (see section 2.2) not even being qualitatively adequate for a description of the chemical system. Typical examples are open-shell transition metal compounds or open-shell singlet states in biological systems but also bond dissociation curves creating openshell fragments. This issue is mostly not relevant for AS-ALD modelling up to now. It might become more pressing when more deposition modelling of metal ALD is carried out. The third, and for AS-ALD most pressing, issue is the failure of many DFs to describe London dispersion interactions. This interaction can be described as the attractive part of the van-der-Waals potential, and it is also often referred to as van-der-Waals forces (although this term is discouraged by experts) or dispersion attraction. The classical physical picture behind this interaction can be drawn as an attraction of induced dipoles. DFs of the first three rungs typically do not describe this interaction since it is intrinsically an electron correlation effect which is not well captured by approaches using one Slater determinant as KS-DFT or HF (see section 2.2.1). This leads to the result, that, e.g., the potential energy curve of the benzene dimer is completely repulsive for PBE and B3LYP. In recent years, it became clear that the failure to describe these interactions leads to large errors in interaction energies especially for non-covalently bound systems (e.g., physisorbed precursors). But also for covalently bound systems, dispersion attraction plays a major, stabilizing role. Several approaches were developed to capture these effects in the framework of DFT. DFs can be parametrized to incorporate these effects in a mean-field approach (e.g., the Minnesota family of functionals), or the non-local electron-electron interactions underlying the dispersion attraction can be incorporated directly into the functionals which leads to the vdW-DFs (e.g., optB88, vdW-DF) . The by far most used approach, also in AS-ALD, is the addition of a correction term to the KS-DFT energy by a semi-empirical scheme. The most common approaches have been initially developed by Grimme (DFT-D) and by Tkatchenko and Scheffler (DFT-TS) . In these approaches, the stabilizing dispersion term is approximated by the pairwise interaction energy of atoms (A and B) in the systems which are then summed up (eq. 2.5). This interaction energy is determined from the polarizability of the atoms in the system expressed via the 𝐶 6 -parameters (the term stems from the perturbation theory approach to intermolecular interaction) considering the decay behavior of this interaction with distance (𝑟 -6 ). In addition, parameters (𝑠 𝑛 ) and so-called damping functions are used to tune the interaction energy to every functional.