Dynamical behavior of the phase transition of strained BaTiO3 from atomistic simulations

Using an atomistic shell model we study the temperature dependence of the ferroelectric properties of BaTiO3 under biaxial compressive strain applicable to growth on perovskites substrate. Molecular dynamics simulations show a 'r→c→p' sequence of phase transitions when temperature is increased, and the absence of an 'ac phase'. The first-order paraelectric-to-ferroelectric phase transition presents in bulk changes to a second-order one as a consequence of the in-plane constraint imposed by the mechanical boundary conditions. From the tetragonal ferroelectric c phase, the transition takes place in a finite range of temperature where the lattice parameter normal to the plane keeps approximately constant until Tc is reached. Analysis of the local polarization behavior reveals an order-disorder dynamics as the dominant mechanism of the transition.