The theoretical description of ferroelectric perovskite materials at finite temperatures is commonly analyzed using Landau-Ginzburg type phenomenological models and Monte-Carlo [MC] or molecular dynamics [MD] simulations. The parametrization of phenomenological potentials originates from experimental data or from first principal calculations [1]. The MC and MD simulations use as a ground zero-temperature energy potentials determined from ab initio calculations. There are commonly used two main approaches, the effective Hamiltonian method [2] and core-shell atomic-level simulations [3].
In this work, we address the structural and polar properties, lattice dynamics and a phase transition sequence of BiFeO3 at finite temperatures using molecular dynamic simulations based on the effective Hamiltonian, which is determined from ab initio calculations, with strain, polarization, and oxygen octahedra tilt degrees of freedom [4]. The ground state energy landscape of the effective Hamiltonian is parametrized up to high orders at degrees of freedom. Such parametrization can precisely characterize the ordered phase and domain wall properties. To characterize the ferroelectric phase transitions we perform the simulations for various temperatures and compare them with outcomes of the core-shell approach [5].
[1] F. Xue, Y. Gu, L.Liang, Y. Wang, and L. Q. Chen, Phys. Rev. B 90, 220101 (2014).
[2] Vanderbilt D. First-principles based modelling of ferroelectrics. Curr.. Opin. Solid State Mater. Sci. (1997) 2:701–5.
[3] M. Sepliarsky, A. Asthagiri, S.R. Phillpot, M.G. Stachiotti, R.L. Migoni, Curr. Opin. Solid State Mater. Sci. 9 (2005) 107.
[4] P. Marton, A. Klic, M. Pasciak, and J. Hlinka: Phys. Rev. B 96, 174110 (2017)
[5] Graf, M., Sepliarsky, M., Machado, R., Stachiotti, M.G.: Solid State Communications, 218, pp. 10-13 (2015)
Multiferroics , Ferroelectrics , Theory and modeling , Dielectric properties
