meV and ΔEspin of -1.46 eV, which are comparable to the reference values of 460 meV and -1.39 eV. On the contrary, apart from SCAN series of functionals, most GGA and meta-GGA functionals severely underestimate both the J and the ΔEspin with a mean relative error of -59% and -45% for the monomer and -50% and -71% for the dimer.