Pressure induced structural phase transition of OsB2: First-principles calculations

Orthorhombic OsB2 was synthesized at 1000 °C and its compressibility was measured by using the high-pressure X-ray diffraction in a Diacell diamond anvil cell from ambient pressure to 32 GPa [R.W. Cumberland, et al. (2005)]. First-principles calculations were performed to study the possibility of the phase transition of OsB2. An analysis of the calculated enthalpy shows that orthorhombic OsB2 can transfer to the hexagonal phase at 10.8 GPa. The calculated results with the quasi-harmonic approximation indicate that this phase transition pressure is little affected by the thermal effect. The calculated phonon band structure shows that the hexagonal P 63/mmc structure (high-pressure phase) is stable for OsB2. We expect the phase transition can be further confirmed by the experimental work.