Intrinsic activation energy for twin-wall motion in the ferroelastic perovskite CaTiO₃

Even in a topologically perfect crystal, a moving twin wall will experience forces due to the discrete nature of the lattice. The potential energy landscape can be described in terms of one of two parameters: the Peierls energy, which is the activation energy for domain wall motion in a perfect crystal; and the Peierls stress, the maximum pinning stress that the potential can exert. We investigate these parameters in a one order parameter discrete Landau-Ginzburg model and a classical potential model of the ferroelastic perovskite CaTiO₃. Using the one order parameter model we show that the Peierls energy scales with the barrier height of the Landau double well potential and calculate its dependence on the width of the wall numerically. In CaTiO₃ we calculate the Peierls energy and stress indirectly from the one order parameter model and directly from the interatomic force field. Despite the simplicity of the one order parameter model, its predictions of the activation energy are in good agreement with calculated values.