High pressure x-ray diffraction studies on solid N2 up to 43.9 GPa

Solid N2 was studied by energy-dispersive x-ray diffraction between 5.75 and 43.9 GPa at room temperature. The transition from δ-N2 (Pm3n) to ε-N2 (R3̄c) was observed at 16.3±0.5 GPa. The pressure-volume curves for both phases were determined. A comparison with the results of a priori calculations shows good agreement up to ∼12 GPa, however, at higher pressures the theoretical isotherm becomes increasingly stiffer.