On the Microscopic Mechanisms behind Ferroelectric Distortion in AgNbO₃

To understand the underlying microscopic mechanisms that drive ferroelectricity in AgNbO 3 , a response‐function calculation of its dielectric and dynamical properties in the paraelectric cubic structure, the precursor to its ferroelectric behavior, is conducted. The results reveal significant charge transfer along the NbO bond, with the Born effective charges for O and Nb atoms surpassing their nominal ionic values, resulting in strong orbital hybridization. Phonon dispersion analysis highlights a soft polar mode at Γ point, confirming the existence of the ferroelectric instability in cubic AgNbO 3 . Inspection of interatomic force constants demonstrates that the destabilizing long‐range dipolar forces, particularly in NbO pairs, together with unstable NbNb interaction, play a central role in inducing the ferroelectric distortion observed in cubic AgNbO 3 and drive the dispersion of the related soft polar mode in phonon dispersion curves. These findings enhance the understanding of the interplay between lattice dynamics and ferroelectricity in AgNbO 3 and underscore its potential in advanced electronic applications.