Parametrization of a phase-field model for ferroelectrics with defects from molecular dynamics data
Dilshod Durdiev
FAU, WW8
24. Mai 2023, 17:00
WW8, Room 2.018-2, Dr.-Mack-Str. 77, Fürth
Ferroelectric material properties are strongly dependent on the microstructural defects, as vacancies, aliovalent dopants and domain and grain boundaries. Experimental investigations show that even a small defect density significantly changes the behavior of the material in response to external fields. Hence, numerical models of ferroelectrics that include localized point defects or averaged continuous defect densities have been developed to take into account their effect in various processes, such as polarization switching and fatigue.
In this study, we develop a parameterization technique to generate input parameters for phase-field simulations of ferroelectric materials using molecular dynamics data. An invariant formulation of the phase-field model for transversely isotropic material behavior is applied, in which spontaneous polarization is considered as the primary order parameter.
Particularly, we present the calibration of the Landau-Devonshire potential and gradient energy coefficients. The domain wall widths (90° and 180°) in the phase-field model, the polarization-field curve and the domain wall kinetics from MD simulations are resolved. Defects are implemented as localized point defects carrying charge, eigenstrain or dipole moment. The three field variables polarization, strain and dielectric displacement are numerically solved by the Fast Fourier Transform as one of the most efficient approaches for treating the interaction of defects.
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