title: Nitrogen oxides under pressure: stability, ionization, polymerization, and superconductivity.
abstract: Nitrogen oxides are textbook class of molecular compounds, with extensive industrial applications. Nitrogen and oxygen are also among the most abundant elements in the universe. We explore the N-O system at 0 K and up to 500 GPa though ab initio evolutionary simulations. Results show that two phase transformations of stable molecular NO2 occur at 7 and 64 GPa, and followed by decomposition of NO2 at 91 GPa. All of the NO(+)NO3(-) structures are found to be metastable at T = 0 K, so experimentally reported ionic NO(+)NO3(-) is either metastable or stabilized by temperature. N2O5 becomes stable at 9 GPa, and transforms from P-1 to C2/c structure at 51 GPa. NO becomes thermodynamically stable at 198 GPa. This polymeric phase is superconducting (Tc = 2.0 K) and contains a -N-N- backbone.
authors.affiliation: College of Materials Science and Engineering, Huaqiao University, Xiamen, 361021 P.R. China.
authors.forename: Dongxu
authors.initials: D
authors.lastname: Li
authors.affiliation: Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, 3 Nobel St., Moscow 143026, Russia.|Department of Geosciences, Stony Brook University, Stony Brook, NY 11794, USA.|Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, Stony Brook, NY 11794, USA.|Moscow Institute of Physics and Technology, 9 Institutskiy lane, Dolgoprudny city, Moscow Region, 141700, Russia.|School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, 710072, China.
authors.forename: Artem R
authors.initials: AR
authors.lastname: Oganov
authors.affiliation: School of Physics and Key Laboratory of Weak-Light Nonlinear Photonics, Nankai University, Tianjin 300071, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Dong
authors.affiliation: Department of Geosciences, Stony Brook University, Stony Brook, NY 11794, USA.|Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, Stony Brook, NY 11794, USA.|School of Physics and Key Laboratory of Weak-Light Nonlinear Photonics, Nankai University, Tianjin 300071, China.
authors.forename: Xiang-Feng
authors.initials: XF
authors.lastname: Zhou
authors.affiliation: Department of Geosciences, Stony Brook University, Stony Brook, NY 11794, USA.|Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Department of Geosciences, Stony Brook University, Stony Brook, NY 11794, USA.|Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: Guangrui
authors.initials: G
authors.lastname: Qian
authors.affiliation: Department of Geosciences, Stony Brook University, Stony Brook, NY 11794, USA.|Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, Stony Brook, NY 11794, USA.
authors.forename: Huafeng
authors.initials: H
authors.lastname: Dong