Table Optimised lattice parameters of the conventional cells of CaTiO 3 , SrTiO 3 , and BaTiO 3 compared to experimental values from the literature. The percentage differences between the calculated and measured values are given in parentheses. BTO has n a = 5 atoms in the primitive cell, resulting in 3n a = 15 branches at each phonon wavevector q q q. CTO and STO have n a = 10 and 20, respectively, and thus considerably more complex phonon spectra with 30 and 60 bands at each q q q. This increase in complexity due to the larger primitive unit cells is compounded by the reduction in symmetry resulting in fewer degenerate bands. The absence of imaginary harmonic modes in all three phonon dispersion curves indicates that the three structures are dynamically stable.