Ligand Field Theory (LFT) provides a detailed explanation of Δ by considering the electrostatic interactions between the metal ion and the surrounding ligands. According to LFT, when ligands approach a transition metal ion, they create an electric field that perturbs the energies of the d-orbitals. In an octahedral field, for instance, the d-orbitals split into two sets: the higher-energy eg and the lower-energy t2g orbitals. The energy gap between these sets is the crystal field splitting energy (Δ).
