We will refer to these different variants of the MBE by the following acronyms in the following: 'iso' is used for the isolated MBE, 'PC' refers to the embedded MBE using point-charge embedding, 'FDE' indicates that an embedded MBE with a frozen-density embedding potential based on the unrelaxed frozen densities of the isolated monomers has been used, whereas 'FDE-ft' denotes the use of a frozen-density embedding potential based on relaxed monomer densities optimized self-consistently in freeze-and-thaw cycles.