title: Structural transformation of molecular nitrogen to a single-bonded atomic state at high pressures.
abstract: The transformation of molecular nitrogen to a single-bonded atomic nitrogen is of significant interest from a fundamental stand point and because it is the most energetic non-nuclear material predicted. We performed an x-ray diffraction of nitrogen at pressures up to 170 GPa. At 60 GPa, we found a transition from the rhombohedral (R3c) epsilon-N(2) phase to the zeta-N(2) phase, which we identified as orthorhombic with space group P222(1) and with four molecules per unit cell. This transition is accompanied by increasing intramolecular and decreasing intermolecular distances. The major transformation of this diatomic phase into the single-bonded (polymeric) phase, recently determined to have the cubic gauche structure (cg-N), proceeds as a first-order transition with a volume change of 22%.
authors.affiliation: Max Planck Institute für Chemie, Postfach 3060, 55020 Mainz, Germany.
authors.forename: M I
authors.initials: MI
authors.lastname: Eremets
authors.forename: A G
authors.initials: AG
authors.lastname: Gavriliuk
authors.forename: N R
authors.initials: NR
authors.lastname: Serebryanaya
authors.forename: I A
authors.initials: IA
authors.lastname: Trojan
authors.forename: D A
authors.initials: DA
authors.lastname: Dzivenko
authors.forename: R
authors.initials: R
authors.lastname: Boehler
authors.forename: H K
authors.initials: HK
authors.lastname: Mao
authors.forename: R J
authors.initials: RJ
authors.lastname: Hemley