High-pressure experiments and first-principles calculations of second-order structural phase transitions

Abstract

The high-pressure study of second-order phase transition of metal dioxides has been performed by both high-pressure experiments and first-principle calculations. In the case of iridium dioxide, the second-order phase transition from the rutile-type to the CaCl2-type structure was not confirmed, because the pyrite-type structure is stable relative to the CaCl2-type structure. In the case of ruthenium dioxide, our study showed that the CaCl2-type structure is metastable, although the second-order phase transition from the rutile-type to the CaCl2-type structure was observed in previous experimental study. The observation of the metastable phase in the previous experiments is due to a significant differential stress in the sample.