Effective Hamiltonian study of PbZr0.95Ti0.05O3 -: art. no. 214111

An effective Hamiltonian H-eff is constructed for PbZr0.95Ti0.05O3. It is parametrized using primarily ab initio results computed in the virtual-crystal approximation. The phase diagram depends sensitively on the energetic competition between the stable orthorhombic antiferroelectric (A(O)) and the metastable "low temperature" rhombohedral ferroelectric (F-R(LT)) structures at 0 K. By incorporating a temperature-dependent thermal-expansion term into H-eff and modifying H-eff to adjust the relative energies of the A(O) and F-R(LT) phases, 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 of the ferroelectric phase.