Structural and thermodynamic properties of OsN₂ from first-principles calculations

We investigate the structural and thermodynamic properties of OsN₂ by a plane-wave pseudopotential density functional theory method. The obtained lattice constant, bulk modulus and cell volume per unit formula are consistent with the available theoretical data. Moreover, the pressure-induced phase transition of OsN₂ from pyrite structure to fluorite structure has been obtained. It is found that the transition pressure of OsN₂ at zero temperature is 67.2 GPa. The bulk modulus B as well as other thermodynamic quantities of fluorite OsN₂ (including the Grüneisen constant \gamma and thermal expansion \alpha) on temperatures and pressures have also been obtained.