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.