Studying the finite temperature properties of ferroelectrics*

ABO₃ perovskite ferroelectrics, as well as their solid solutions, exhibit rich transitional behavior patterns that can be exploited, e.g., to obtain large piezoelectric and dielectric responses. Due to the complexity of the phase diagrams of these materials, mesoscale-level parameterizations capable of accurately reproducing their finite temperature properties are difficult to develop. Furthermore, obtaining such parameters from first principles calculations is complicated by the large number of available exchange correlation (XC) functionals. We investigate the influence of XC functionals on the prediction accuracy of ferroelectric phase transitions in PbTiO₃. LDA, PBE, PBEsol and vdW-DF-C09 XC functionals are evaluated utilizing constant-temperature molecular dynamics, in comparison with Wang-Landau (WL) Monte Carlo and Replica Exchange WL simulations. We find that LDA, PBEsol and vdW-C09 provide good estimates of physical properties near the phase transition, as compared with experiments, while PBE significantly overestimates the transition temperature.