Intrinsic electrocaloric effect in ferroelectric alloys from atomistic simulations

Electrocaloric effect (ECE) in (Ba0.5Sr0.5)TiO₃ ferroelectric alloys is calculated from first principles using a computational scheme that combines canonical and microcanonical Monte Carlo simulations. Our results are in very good agreement with the available experimental data and reveal many intriguing features of ECE including; (i) a significant enhancement of the ECE in paraelectric phase, (ii) nearly linear reversible temperature change associated with the electric field variation up to extremely large fields and, (iii) a possibility of achieving large ECE at room temperatures. Our atomistic insight suggests that in ferroelectrics ECE is caused by the redistribution of the entropy between the part associated with the dipoles' order and the part associated with the order in the kinetic energies of atomic vibrations. This mechanism can also be viewed as a ``conversion'' of spatially inhomogeneous dipole distribution into spatially inhomogeneous temperature distribution.