Electrocaloric effect in BaTiO3: A first-principles-based study on the effect of misfit strain

We address the question of how the electrocaloric effect in epitaxial thin films of the prototypical ferroelectric BaTiO3 is affected by the clamping to the substrate and by substrate-induced misfit strain. We use molecular dynamics simulations and a first-principles-based effective Hamiltonian to calculate the adiabatic temperature change Delta T under different epitaxial constraints. Our results demonstrate that, consistent with phenomenological theory, clamping by the substrate reduces the maximum Delta T compared to bulk BaTiO3. On the other hand, compressive misfit-strain leads to a strong increase of Delta T and shifts the maximum of the electrocaloric effect to higher temperatures. A rather small compressive strain of -0.75% is sufficient to obtain a Delta T that is larger than the corresponding bulk value. (C) 2014 AIP Publishing LLC.