𝐸 𝑓,𝑏𝑢𝑙𝑘 = 𝐸 𝑖𝑛𝑡 + 𝐸 𝑐𝑜𝑚𝑝 (10) 𝐸 𝑓,𝑠𝑙𝑎𝑏 = ∆𝐸 𝑆 + 𝐸 𝑖𝑛𝑡 + 𝐸 𝑐𝑜𝑚𝑝 (11) where ES denotes the difference in surface energies of the final slab (ES,fin) and of the initial slab (ES,in), respectively (see also section S1 in the Supporting Information (SI)). Hence, the two formation energies differ in such a way that in the second case also changes in the surface energies will be included in the formation energies, which may be much larger than, e.g., contributions from interface or compression energies in the bulk. This will be illustrated in more detail in the following section. Here it should also be noted that all energy changes occurring upon cleaving the bulk crystal are attributed to the surface energy, meaning that the interface energy and the compression energy in the bulk and in the slab are considered to be identical. aware of the fact that experimentally only Ag monolayer films were found to grow pseudomorphically, while for bilayer and thicker films strain relief results in the formation of a unidirectionally expanded (striped) phase or, upon annealing, in a trigonal incommensurate phase, where strain is relieved isotropically. Nevertheless, the data derived here provide detailed insight in stability trends.