Pressure dependence of the crystal structure of SrCeO3 perovskite

The crystal structure of SrCeO3 perovskite, orthorhombic, space group Pmcn, has been determined from Rietveld profile refinement of neutron, time-of-flight, powder diffraction data at four pressures between 0 and 7.9 GPa. The unit cell compression behaviour is anisotropic with κa = 3.14(8) × 10−3 GPa−1, κb = 3.18(8) × 10−3 GPa−1 and κc = 1.78(6) × 10−3 GPa−1, and fitting the pressure dependence of the unit cell volume using a second-order Birch-Murnaghan equation of state, the bulk modulus has been determined as 110.1(6) GPa. Contrary to a model based on EXAFS results, which predicts octahedral tilting as the dominant compression mechanism in perovskites with excess A-site volume, SrCeO3 undergoes bond compression with increasing pressure in agreement with the results obtained in a recent Raman investigation. SrCeO3 behaves atypically when compared to other AIIBIVO3 perovskites in both temperature and pressure, which is attributed to the magnitude of the CeO bond length.