Ferroelectric materials contain domains of ordered electric dipoles, separated by domain walls, that can undergo polarisation switching under externally applied electric fields. The domain switching dynamics in ferroelectric materials plays an essential role in their application to electronic and electro-optic de- vices. Previous studies suggest that the switching occurs largely through domain wall motion which is explained from the viewpoint of statistical physics on surface growth as the behaviour of a pinned elas- tic interface. We perform molecular dynamics simulations to investigate the domain switching process and quantitatively estimate the switching speed of anti-parallel 180° domains in ferroelectric, tetragonal BaTiO3 perfect single crystals at room temperature using the core-shell model. We observe an unprece- dented, non-linear increase in the domain switching speed caused by the nucleation of new domains within the switching domain. We determine the strength of the electric field to evoke nucleation of new domains and show that the nucleated domains diffuse into nearby favourable domains when the electric field is removed. Furthermore, we discuss the prominence of domain nucleations during ferroelectric switching.
Ferroelectric functional materials improved tremendously over the last decades. Therefore not only the material science regarding material manufacturing but also simulation models and algorithms have been developed further. There are two fundamentally different types of models available. Firstly, particle based models describe material as a discrete particle system. Secondly, continuum mechanics describe material as a continuum. Both continuum mechanics and the particle based methods have their benefits and disadvantages. Still the main disadvantage of particle based methods are the enormous computational costs. In this work the fundamentals of a molecular statics algorithm for the simulation of ferroelectric functional materials are elucidated in order to reduce the computational costs. Furthermore barium titanate has been simulated in order to demonstrate the applicability of the molecular statics algorithm. Since the computational costs of molecular statics are highly reduced compared to other atomistic algorithms larger systems can be calculated more efficiently.
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