Negative vibrational shift of nitrogen diluted in xenon at the fluid–solid transition

Formation of xenon-nitrogen compounds at high pressure

Molecular nitrogen exhibits one of the strongest known interatomic bonds, while xenon possesses a closed-shell electronic structure: a direct consequence of which renders both chemically unreactive. Through a series of optical spectroscopy and x-ray diffraction experiments, we demonstrate the formation of a novel van der Waals compound formed from binary Xe-N₂ mixtures at pressures as low as 5 GPa. At 300 K and 5 GPa Xe(N₂)₂-I is synthesised, and if further compressed, undergoes a transition to a tetragonal Xe(N₂)₂-II phase at 14 GPa; this phase appears to be unexpectedly stable at least up to 180 GPa even after heating to above 2000 K. Raman spectroscopy measurements indicate a distinct weakening of the intramolecular bond of the nitrogen molecule above 60 GPa, while transmission measurements in the visible and mid-infrared regime suggest the metallisation of the compound at ~100 GPa.

Highly repulsive interaction in novel inclusion D2-N2 compound at high pressure: Raman and x-ray evidence

We present spectral and structural evidences for the formation of a homogeneous cubic δ-N(2)-like, noncrystalline solid and an incommensuratelike hexagonal (P6(3)22) inclusion compound (N(2))(12)D(2), formed by compressing a nitrogen-rich mixture to 5.5 and 10 GPa, respectively. A strong repulsive coupling in (N(2))(12)D(2) is evident from a blue shift, discontinuous changes, and the absence of turnover of the D(2) vibron to 70 GPa--all in sharp contrast to both pure D(2) and other inclusion compounds. This repulsive interaction is responsible to the observed incommensuratelike structure and large internal pressure.