Pressure-induced volume collapse and structural phase transitions in SrRuO3

• Crystal structure of SrRuO3 was studied under high pressure up to 54 GPa.
• Pv to monoclinic to triclinic sequence of phase transitions was observed.
• Transition to triclinic phase at ∼38 GPa is accompanied by a 3.5% volume collapse.
• Volume collapse in SrRuO3 is not driven by a change in Ru valence state.
• Pv-to-pPv phase transition predicted by DFT at 40 Gpa is not observed up to 54 GPa.

We report on the low temperature (6 K) structural properties of SrRuO3 under quasi-hydrostatic pressure studied by synchrotron X-ray powder diffraction in a diamond anvil cell. First principle calculations predict a first-order perovskite (Pv) to post-perovskite (pPv) phase transition at ∼40 GPa accompanied by a 1.9% volume collapse. Our results rule out the occurrence of a pPv phase to 54 GPa. Instead, we find a Pv to monoclinic to triclinic sequence of phase transitions. The monoclinic to triclinic phase transition at ∼38 GPa is accompanied by a 3.5% volume collapse. X-ray absorption spectroscopy indicates that this volume collapse is not accompanied by a change in Ru valence state. Our results should help guide improvements to theoretical treatments of this and other correlated d-electron systems based on density functional theory.

Unit cell volume as a function of pressure (T=6 K). Black squares and red circles correspond to Ne and He pressure media, respectively. Blue dashed lines are fit to the data before the volume collapse using a second-order Birch–Murnaghan equation of state excluding (lower curve) and including (upper curve) neutron diffraction data for the low temperature, ambient pressure volume. Dashed lines denote structural phase boundaries.Figure optionsDownload as PowerPoint slide