Insight into Pyroelectricity and Phase Transitions in Ferroelectrics from Nonequilibrium Approach: The Case of PbTiO₃

Abstract

Computational methodology is proposed to simulate time dependent temperature variations via thermostat approach. The methodology is applied to study pyroelectricity under nonequilibrium conditions in prototypical ferroelectric PbTiO 3 . It is found that at room temperature the nonequilibrium effects in pyroelectricity begin manifesting above 1.0 THz and originate from the overlap with the intrinsic soft mode frequency. Therefore, the proposed computational methodology can be used to predict equilibrium pyroelectric response by choosing a frequency of temperature variation below the intrinsic polar mode frequencies for the material. Probing the dynamics of ferroelectric phase transition with the proposed methodology revealed that it takes about a nanosecond for the computational supercell to undergo phase transition. It is concluded that computational techniques capable of simulating picoseconds can be used to compute pyroelectric response from nonequilibrium dynamical approach while those that can reach nanoseconds are suitable for simulating phase transitions in ferroelectrics.

Pyroelectric Effect in Tetragonal Ferroelectrics BaTiO3 and KNbO3 Studied with Density Functional Theory

“…To the best of our knowledge, the first atomic-level modeling study on pyroelectricity was done by Peng and Cohen, who used a first-principles-based shell model potential along with molecular dynamics (MD) for LiNbO 3 . A more recent example of employing ab initio MD for the study of pyroelectricity has been reported by Ponomareva et al for pyroelectric response and phase transitions in PbTiO 3 . Machine-learned force fields combined with MD simulations have likewise been used to study piezoelectricity and pyroelectricity in ZrO 2 by Kersch et al The converse effect of the pyroelectric effect and electrocaloric effect has also been studied with effective Hamiltonians combined with MD simulations in lead zirconate titanate Pb­(Zr 1– x Ti x )­O 3 (PZT), , barium zirconate titanate Ba­(Zr 1– x Ti x )­O 3 (BZT), and barium titanate BaTiO 3 , − for example.…”