Polymorphism of polymeric nitrogen at high pressures

Polymeric nitrogen at 120 GPa–180 GPa is known in two monatomic crystalline cubic gauche (cg-N) and layered polymeric (LP-N) phases and one amorphous modification (η-N), and all these high-pressure phases attract considerable attention for their potential application as a high energy density materia...

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Bibliographic Details
Published in:The Journal of chemical physics 2020-06, Vol.152 (24), p.244502-244502
Main Authors: Cheng, Peng, Yang, Xue, Zhang, Xiao, Wang, Yu, Jiang, Shuqing, Goncharov, Alexander F.
Format: Article
Language:English
Subjects:
Diamond anvil cells
Flux density
Laser beam heating
Lasers
Nitrogen
Physics
Polymorphism
Room temperature
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Summary:Polymeric nitrogen at 120 GPa–180 GPa is known in two monatomic crystalline cubic gauche (cg-N) and layered polymeric (LP-N) phases and one amorphous modification (η-N), and all these high-pressure phases attract considerable attention for their potential application as a high energy density material. Here, we investigated the stability of these modifications at high pressures in the laser heated diamond anvil cell upon decompression from 161 GPa. Pure LP-N was synthesized above 152 GPa upon laser heating of η-N to 2500 K, while cg-N forms below 150 GPa. Upon laser heating at 129 GPa and 123 GPa, the LP-N clearly diminished, indicating that the synthesis of cg-N becomes more favorable in a mixed phase region below 129 GPa. Upon unloading, cg-N and LP-N were metastable to at least 71 GPa at up to 2500 K and at room temperature, respectively. These observations clarified a complicated polymorphism of monatomic nitrogen at high pressures and large hysteretic phenomena related to a transition to nonmolecular nitrogen.
ISSN:0021-9606
1089-7690
DOI:10.1063/5.0007453