Pressure dependence of instabilities in perovskite PbZrO3 Original Research Article

We have computed the frequencies of selected normal modes in perovskite PbZrO3 (PZ) as a function of lattice parameter using local density-functional theory variational linear response. The harmonic instabilities of the perovskite structure which freeze in to give the orthorhombic antiferroelectric (AFE) phase in PZ and the low-temperature rhombohedral ferroelectric (FE) phase in PbZr1−xTixO3 (PZT) all become more unstable under pressure. The most unstable AFE Σ3 mode destabilizes more rapidly under pressure than the unstable zone center polar mode. This provides an explanation for the observed FE–AFE transition in (modified) Zr-rich PZT under applied pressure.