In ionic or polar solids, long-range Coulomb interactions lead to a significant separation between the longitudinal optical (LO) and transverse optical (TO) phonon modes at and near the zone center (⃗ q → 0), leading to LO-TO splitting near the Γ point. To accurately represent the phonon dispersion in such systems, a non-analytic correction (NAC) term should be included, which accounts for the macroscopic electric field generated by the relative displacements of charged ions.