Chemical evolution in nitrogen shocked beyond the molecular stability limit

RK Lindsey and S Bastea and Y Lyu and S Hamel and N Goldman and LE Fried, JOURNAL OF CHEMICAL PHYSICS, 159, 084502 (2023).

DOI: 10.1063/5.0157238

Evolution of nitrogen under shock compression up to 100 GPa is revisited via molecular dynamics simulations using a machine-learned interatomic potential. The model is shown to be capable of recovering the structure, dynamics, speciation, and kinetics in hot compressed liquid nitrogen predicted by first-principles molecular dynamics, as well as the measured principal shock Hugoniot and double shock experimental data, albeit without shock cooling. Our results indicate that a purely molecular dissociation description of nitrogen chemistry under shock compression provides an incomplete picture and that short oligomers form in non-negligible quantities. This suggests that classical models representing the shock dissociation of nitrogen as a transition to an atomic fluid need to be revised to include reversible polymerization effects.

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