Finally, destabilizing terms mainly arise from Pauli repulsion; however, the covalent complexes involve geometrical preparation energies EPREP due to the required orbital hybridization sp 2 →sp 3 of fullerenes and rearrangements of phosphorene sublattices, which equals to contributions of 10-16% to the destabilizing energy. The root-mean-square deviation RMSD of the fullerene geometries in the complex ranges from 0.04 to 0.94 Å with respect to the free molecules, which increase with the order of cycloaddition reaction. Although there is an energy penalty due to weak structural changes to reach the covalent bonding, the low RMSD values show that the electronic/structural rearrangements are low-scale and are not prohibited.