Hydronitrogen oxides at high pressures

Hydrogen-rich materials have been identified as potential high temperature superconductors following the discovery of record-high T_c in the hydrogen sulfide system at high pressures near 200 GPa. Water-ice H₂O is chemically similar to hydrogen sulfide but is an insulator below 1 TPa. It has been recently suggested that substitution of nitrogen for oxygen into the crystal lattice phase X of water-ice might result in induced superconductivity of water/ice. In order to determine whether the proposed compounds are chemically stable, and if not, whether other hydronitrogen oxide superconductors exist, the ternary H_xN_yO_z crystal structure search is performed at high pressures. The ternary H-N-O phase diagram is constructed and the several stable and metastable HNO compounds are found. The chemical pathways involving pressure-induced deprotonation of suitable hydronitrogen hydrades are considered. The electronic and vibrational properties of these new compounds are analyzed and their potential for observation of superconductivity of these hydronitrogen oxides is discussed.