First principles-based calculation of the electrocaloric effect in BaTiO${}_3$: comparison between direct and indirect methods

Abstract

We use molecular dynamics simulations for a first principles-based effective Hamiltonian to calculate two important quantities characterizing the electrocaloric effect in BaTiO${}_3$, the adiabatic temperature change $\Delta T$ and the isothermal entropy change $\Delta S$, for different electric field strengths. We compare direct and indirect methods to obtain $\Delta T$ and $\Delta S$, and we confirm that both methods indeed lead to identical result provided that the system does not actually undergo a first order phase transition. We also show that a large electrocaloric response is obtained for electric fields beyond the critical field strength for the first order phase transition. Furthermore, our work fills several gaps regarding the application of the first principles-based effective Hamiltonian approach, which represents a very attractive and powerful method for the quantitative prediction of electrocaloric properties. In particular, we discuss the importance of maintaining thermal equilibrium during the field ramping when calculating $\Delta T$ using the direct method within a molecular dynamics approach.

10 pages, 6 Figures, 1 Table

References in corpus (4)

• Advanced materials for solid-state refrigeration
• Giant electrocaloric effect around T${}_c$
• First-principles accurate total-energy surfaces for polar structural distortions of BaTiO3, PbTiO3, and SrTiO3: consequences to structural transition temperatures
• Electrocaloric effect in BaTiO${}_3$: a first-principles-based study on the effect of misfit strain

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