ALD precursors have to fulfill a set of properties which have been summarized in the ALD literature. The most important factors are: (i) stability against decomposition in the gas phase, (ii) reactivity towards the substrate and (iii) significant vapor pressure under ALD conditions. Precursor stability is not specific for AS-ALD approaches and has been treated in the ALD literature for a range of precursors. The (selective) reactivity towards the substrate(s) will be treated in section 3.3.1. This leaves vapor pressure to be discussed here although it is also not specific for AS-ALD. Most computational approaches rely on quantitative structure-property relationships (QSPR) or group-contribution (GC) approaches. They are intrinsically empirical and lack predictive power. Ab initio simulations are complicated by the need to properly describe the gas as well as the liquid phase. Recently, a computational workflow based on quantum mechanically derived force fields (QMDFF) was presented which allows the vapor pressure prediction for a range of (AS-)ALD precursors with good accuracy. However, considering the monomer-dimer equilibrium of group 13 precursors (see section 3.1.1) is not yet possible. It can be expected that further development in the field of machine learning will make the prediction of complex properties like vapor pressure more reliable in the future.