The crystal field stabilisation energy is defined as the energy difference of electronic configurations in the ligand field (ELF) and the isotropic field (Eiso).
CFSE (ΔE0) = {E LF} – {Eiso }
= {nt2g (-0.4) + n6g (0.6) Δ0 – npP} – {n’p P}
Here ntg is the number of electrons in t, orbitals
neg is the number of electrons in e orbitals
np is the number of electrons in the ligand field
n’p is the number of electrons in the isotropic field
