The charge transfer is the dominant stabilizing physical effect, this is inter-fragment orbital interactions play a key role in the stability of doped phosphorene materials. For instance, the ECT values in the substitutionally-doped TMSPhos systems are in the range of -8.89 to -4.65 eV (Table ). Since ECT is related to the magnitude of the donor-acceptor orbital interactions responsible for a net charge flow between molecular fragments, the NBO analysis was used to locate the interactions between occupied and unoccupied orbitals. In this way, the magnitude of the ECT term is related to a mixture of electron delocalization from the occupied (bonding) orbitals of phosphorene to the unoccupied (antibonding) acceptor orbitals of metal atoms [such as dLP*, pLP* and d Rydberg (RY*)]. Occupied donor orbitals of phosphorene are bonding P-P orbitals (the so-called BD orbitals), sp lone pairs (the so-called LP orbitals), and s-core orbitals (the socalled CR or non-valence orbitals).