A finite phosphorene nanosheet (P125H30) was adopted (surface size of ⁓440 Å 2 and volume of ⁓1012 Å 3 ), where the dangling bonds at the edges were saturated with hydrogen atoms to avoid vacant orbitals. The selection of this model is based on the local nature of the doping and well-converged dopant binding energies; also, a molecular model allows to use an extended allelectron basis set, and it is required for the implemented binding and energetic analysis in this work (see below). Two doping schemes were modeled: substitutionally (S) doped phosphorene (TM-P125H30, abbreviated as TMSPhos), and adatom-doped phosphorene (TM-P126H30, abbreviated as TMAPhos) (Fig. ). Third-row transition metals (Sc-Zn) were adopted as dopants.