Kim et al. found the dimerization of dimethyl-aluminum isopropoxide (DMAI) to be the major factor for the high deposition selectivity compared to trimethylaluminum (TMA) when using ethanethiol as inhibitor. They used DFT approaches (B97-D3/def2-SVP) to compute the dimer dissociation enthalpy of TMA to be 85.4 kJ•mol -1 which was found to be close to the experimental enthalpy change of the reaction (ca. 83 kJ•mol -1 ) . Only 2% of the precursor exists as dimers under the ALD conditions modelled (T = 150 °C, p = 1.3 mbar) which corresponds to DDF = 98%. In contrast, DMAI shows a dimer dissociation enthalpy of 267.3 kJ•mol -1 which leads to a negligible DDF (10 -8 %). The authors assumed the same entropy of dissociation and based their conclusions on enthalpy changes (ΔH). The effect of this dimerization on the adsorption of DMAI on Al2O3 has very recently been investigated using MLPs. The dimerization energy was computed with DFT approaches (PBE-D3(BJ), 450 eV, VASP) to 239 kJ•mol -1 (DMAI) and 94 kJ•mol -1 (TMA). The MLP values were ca. 10 kJ•mol -1 higher. Already from these examples, it becomes clear that different DFT approaches can lead to values differing by 10-30 kJ•mol -1 , depending on the choice of the specific setup (density functional, basis set). This question of "validation" has recently been addressed for precursor dimerization by computing the values at the highly accurate CCSD(T) level with complete basis set (CBS) extrapolation, thus eliminating major error sources. In agreement with previous computational studies, aluminum alkyl precursors were found to be monomeric, while tris(dimethylamino)aluminum (TDMAA) and DMAI are dimeric under typical ALD conditions. The chlorinated aluminum alkyls are partly dissociated depending on temperature and pressure. The influence of precursor dimerization has not yet been investigated for intrinsically selective approaches where the different reactivity of monomeric and dimeric forms could be used to discriminate between two surfaces, e.g., when one can open the dimer and the other one cannot.