Remarkable stability of γ-N2 and its prevalence in the nitrogen phase diagram
Year: 2024
Authors: Yan J.W., Dalladay-Simpson P., Conway L.J., Gorelli F., Pickard C., Liu X.D., Gregoryanz E.
Autors Affiliation: Chinese Acad Sci, Key Lab Mat Phys, Inst Solid State Phys, HFIPS, Hefei 230031, Peoples R China; Ctr High Pressure Sci & Technol Adv Res, Shanghai, Peoples R China; Univ Edinburgh, Ctr Sci Extreme Condit, Edinburgh, Scotland; Univ Edinburgh, Sch Phys Astron, Edinburgh, Scotland; Univ Sci & Technol China, Hefei, Peoples R China; Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England; Tohoku Univ, Adv Inst Mat Res, Sendai 9808577, Japan; CNR, Ist Nazl Ottica, Via Nello Carrara 1, I-50019 Sesto Fiorentino, FI, Italy.
Abstract: Solid nitrogen exhibits a panoply of phenomena ranging from complex molecular crystalline configurations to polymerization and closing band gap at higher densities. Among the elemental molecular solids, nitrogen stands apart for having phases, which can only be stabilized following particular pressure-temperature pathways, indicative of metastability and kinetic barriers. Here, through the combination of Raman spectroscopy and dynamic compression techniques, we find that the appearance of the whole nitrogen phase diagram is determined by the P-T paths taken below 2 GPa. We reveal the existence of the path- and phase-dependent triple point between the beta – N-2, delta(loc)-N-2 and gamma- or epsilon-N-2. We further show that the beta-N-2 towards gamma-N-2 path below the triple point, that evades delta(delta(loc))-N-2, results in the formation of gamma-N-2, which in turn becomes a dominant phase. We then demonstrate, that the beta-N-2 through delta(delta(loc))-N-2 above the triple point path leads to the formation of epsilon-N-2 and the well-established phase diagram. An additional pathway, which by-passes the rotationally inhibited modifications delta(delta(loc))-N-2, via rapid compression is found to produce gamma-N-2 at higher temperatures. We argue that the pathway and phase sensitive triple point and the compression rate dependent phase formation challenge our understanding of this archetypal dense molecular solid.
Journal/Review: SCIENTIFIC REPORTS
Volume: 14 (1) Pages from: 16394-1 to: 16394-8
More Information: This work was supported by Youth Innovation Promotion Association of CAS (No. 2021446), the National Science Foundation of China (Grants No. 11874361, No. 11404343, No. 51672279), the CAS Innovation Grant (Grant No. CXJJ-19-B08), Anhui key research and development program (2022h11020007) and the HFIPS Director’s Fund of CAS (Nos. BJPY2022B02, YZJJ202102, YZJJ-GGZX-2022-01, 2021YZGH03). J.W. Yan is grateful for the support from M. Pena-Alvarez through her UKRI Future Leaders Fellowship (Mrc-Mr/T043733/1).KeyWords: High-pressure Phases; X-ray-diffraction; Raman-spectroscopy; Structural Diversity; Transitions; Compression; Hydrogen; Kinetics; GpaDOI: 10.1038/s41598-024-66493-0Citations: 1data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-12-22References taken from IsiWeb of Knowledge: (subscribers only)