An effective Hamiltonian is constructed for PbZr0.95Ti0.05O3. It is parameterized using ab initio results computed in the virtual crystal approximation. The phase diagram depends sensitively on the energetic competition between the stable orthorhombic antiferroelectricand the metastable low temperature rhombohedral ferroelectric structures at zero Kelvin. By fitting chiefly to the ab initio structures and by incorporating a temperature dependent lattice expansion term, we obtain a ferroelectric phase intervening between the low temperature antiferroelectric ground state and the high temperature paraelectric phase,in qualitative agreement with experiments. We also discuss the temperature-dependent disordering of the oxygen octahedral tilts responsible for the experimentally observed space group in the ferroelectric phase.
Physical Review B (Condensed Matter and Materials Physics)
ab initio phase diagrams, effective Hamiltonians, ferroelectric transitions, lead zirconate titanate, PZT