Study The Evolution Process Of Domain Structure In Ba TiO₃ Thin Film By Molecule Dynamics Simulations

Ferroelectric materials have excellent mechanical and electric coupling characteristics so that it is widely applied in aviation,automobile industry,medicine and microelectronics such as sensor,actuator,transducer.They are proposed and developed as one of the main functional materials in recent 20 years.With the gradual development of miniaturization of ferroelectric devices,the characteristic size of materials is decreasing,so that there are some phenomena which are different from the traditional size.Because in nanoscale,polar domain structure will exhibit some special polar structure and evolution behavior.Therefore,it is significant to study the domain evolution in different conditions for ferroelectric device design.?1?In this paper,core-shell model of titanate barium crystals is proposed,the interaction potential and potential parameters of each particle are given,the method of calculating the intensity of polarization and toroid moment are described.?2?Using molecular dynamics to simulate domain evolution of BaTiO₃ single crystal thin film under compression strain in different thickness of domain.The research shows that the thickness of domain has a significant influence on the polarization vortex such as type,scale,quantity and stability in the process of uniaxial compressive strain.The toroid moment corresponds to the evolution of polarization structure.The 90^o stripe domain is stable in specific thickness of domain.It can be used to help design novel and stable ferroelectric devices.Within certain limits of strain,the thickness of domain have little effect on mechanical behavior of BaTiO₃ single crystal nanofilm.?3?Using molecular dynamics to simulate domain evolution of BaTiO₃ single crystal nanofilm under compression strain in different stripe domain directions.The research shows that when the strain loading direction is parallel to 180°stripe domain.The domain structure can evolve into different polarization structure and produce vortex and anti-vortex structure.when the strain loading direction is perpendicular to 180°stripe domain,because of the pining behavior of 90°stripe domain 180°stripe domain structure is always stable and have not a sudden change in the process of evolution.The polarization structure corresponds to the intensity of polarization.The evolution of polarization vortex corresponds to the toroid moment.It verifies that toroid moment can describe the evolution of polarization structure in ferroelectric materials.