Fig. 6: Comparison of phonon spectral function and SCP+bubble dispersions.

Phonon spectral function Aq(ω) of a cubic KNbO3 for T = 800 K and b cubic NaNbO3 for T = 1000 K calculated with V = VDFT. SCP dispersions with bubble self-energy correction (SCP+bubble) from the QP approximation are also presented as white solid lines.