Fig. 8: Frequency-dependent dielectric response of cubic BaTiO3 at 250 K computed with a 6 × 6 × 6 supercell.
From: Thermodynamics and dielectric response of BaTiO3 by data-driven modeling

The imaginary part of the spectrum is fitted to a sum of two simple harmonic oscillator response functions, as in ref. 25; the two separate oscillator responses are shown in thin light blue lines, while the fitted sum is shown as a thick light blue line.