DFT studies on ferroelectric ceramics and their alloys: BaTiO₃, PbTiO₃, SrTiO₃, AgNbO₃, AgTaO₃, Pb_xBa_1-xTiO₃ and Sr_xBa _1-xTiO₃

Aiming at a presentation of the utility of the state of art of first-principles methods (PBE flavor of Density Functional Theory, DFT) in the area of materials science and engineering, we present our studies of the equation of state and ferroelectric-paraelectricphase transition in several ferroelectric systems, including BaTiO₃, PbTiO₃, SrTiO₃, AgNbO₃, Pb_xBa_1-xTiO ₃ and Sr_xBa_1-xTiO₃. We also report the Born effective charges, optical dielectric constant, and phonon dispersion relation properties from Density Functional Perturbation Theory. Computed results are compared with other theoretical results (which were mostly on BaTiO₃, PbTiO₃, cubic SrTiO₃) using various approaches, as well as experiments. The studies on AgNbO₃ and alloys are the first calculations to the best of our knowledge. The predictions obtained by DFT studies presented are in good agreement with the experimental results.