Ab Initio Thermodynamics of Ferroelectrics: The case of PbTiO3

ORAL

Abstract

We report a molecular dynamics study of the ferroelectric phase transition in PbTiO3 using deep neural networks, trained on first-principles SCAN-DFT data, to represent potential and polarization surfaces [1,2]. Our approach includes anharmonic effects beyond the limitations of reduced models and of the linear approximation for the polarization. An external isotropic pressure of ~28 kbar was applied to correct for the overestimate of the tetragonality by the SCAN functional. The calculated enthalpy, spontaneous polarization, specific heat and dielectric susceptibility agree well with experiments on single domain crystals. In addition, we studied how the free energy depends on the polarization with enhanced sampling methods, further supporting the first-order character of the transition.

[1]L. Zhang, J. Han, H. Wang, R. Car, and W. E, Phys.Rev. Lett., 120, 143001 (2018)

[2]L. Zhang, M. Chen, X. Wu, H. Wang, W. E, and R. Car, Phys. Rev. B, 102, 041121 (2020)

*This work was supported by the Computational Chemical Sciences Center: Chemistry in Solution and at Interfaces (CSI) funded by DOE Award DE-SC0019394 and a gift from iFlytek to Princeton University. This work used computational resources of the National Energy Research Scientific Computing Center (NERSC) and also resources managed and supported by Princeton Research Computing.

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Presenters

  • Pinchen Xie

    • Princeton University

Authors

  • Pinchen Xie

    • Princeton University

  • Yixiao Chen

    • Princeton University

  • Weinan E

    • Princeton University

  • Roberto Car

    • Princeton University