Kahn and Briat developed a model based on the Heitler-London valence bond theory to relate the magnetic coupling to the exchange interaction term (K ab , ferromagnetic coupling), the overlap of magnetic orbitals (S ab ), and an effective one-electron operator (β = ⟨a| ĥ (1) |b⟩, antiferromagnetic coupling). J ab = 2K ab + 4βS ab (3) An alternative approach to decompose magnetic interactions was proposed by Hay, Thibeault, and Hoffmann who use symmetry-adapted magnetic orbitals (ϵ g/u ): 12