We determine the relative thermodynamic stability of competing homogeneously and inhomogeneously ordered ferroelectric phases of PbTiO 3 using its free-energy landscape, obtained from constrained- polarization molecular-dynamics simulations with a first-principles effective Hamiltonian and thermodynamic integration. While we find that the tetragonal structure is thermodynamically most stable at temperatures below the ferroelectric transition temperature (T0=660 K), the free energy of an "orthorhombic-like" 90â̂̃ domain phase relative to the tetragonal phase almost vanishes at T=540 K and remains small at all temperatures below T0. In contrast to BaTiO3, the 90â̂̃ domain structure is an order of magnitude lower in energy than the one with 180â̂̃ domains. We show that the dielectric response contains signatures of such a domain structure and is significantly stronger than that of the uniformly polarized tetragonal phase of PbTiO3.
|Physical Review B - Condensed Matter and Materials Physics
|Published - Jan 22 2013
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics