Engineering BaTiO₃ Based Ferroelectric Materials with Reactive Molecular Dynamics Simulations

Ferroelectric materials such as barium titanate (BaTiO₃) have wide applications in nano scale electronic devices due to their outstanding properties. In this study, we developed a ReaxFF reactive force field for BaTiO₃ which can reproduce the ferroelectric/non-ferroelectric phases, ferroelectric and thermal hysteresis loops of the BaTiO₃ crystal structure and O-vacancy, Ba-O and Ti-O divacancy formation energies and their migration. This ReaxFF description can be straightforwardly extended to a wide range of material interfaces. The force field predicted that a 4.8 nm sample thickness is required to observe the ferroelectric hysteresis effect. Also, we found that oxygen vacancies (OVs) in the BaTiO₃ cluster reduce the polarization and the phase transition temperature. Our BaTiO₃ ReaxFF reactive force field showed an outstanding ability of predicting the domain walls in BaTiO₃. We investigated effect of the defect (O-vacancy, divacancy) densities as well as the thichkness on the ferroelectric hysteresis loops of the BaTiO₃ thin film structures to lead design efforts of novel BaTiO₃ based ferroelectric materials.