Quasicontinuum study of 180 degree domain walls and cracks in tetragonal phase BaTiO3

Complex lattice Quasicontinuum theory is applied to simulations of phenomena in tetragonal phase BaTiO₃. Quasicontinuum theory is a multiscale theory, which bridges a unified continuum and atomistic description of materials at the same time. Handling millions of atoms simultaneously, Quasicontinuum derives the description of the materials directly from the underlying atomistics. Two phenomena are being investigated: a 180 degree wall and a crack under quasistatic loading. We obtain a very small atomistic thickness of the wall, but we also see long ranging effects emerging from the wall´s presence, which have not been seen in the previous molecular dynamics studies. We are able to find equilibrium solutions for a crack under increasing load. We see characteristic polarization changes appearing around the crack tip.