Evidence for Crystalline Structure in Dynamically-Compressed Polyethylene up to 200 GPa

Evidence for Crystalline Structure in Dynamically-Compressed Polyethylene up to 200 GPa

Hartley, N. J.; Brown, S.; Cowan, T.; Cunningham, E.; Döppner, T.; Falcone, R. W.; Fletcher, L. B.; Frydrych, S.; Galtier, E.; Gamboa, E. J.; Laso Garcia, A.; Gericke, D. O.; Glenzer, S. H.; Granados, E.; Heimann, P. A.; Lee, H. J.; Macdonald, M. J.; Mackinnon, A. J.; Mcbride, E. E.; Nam, I.; Neumayer, P.; Pak, A.; Pelka, A.; Prencipe, I.; Ravasio, A.; Rödel, M.; Rohatsch, K.; Saunders, A. M.; Schölmerich, M.; Schörner, M.; Schuster, A. K.; Sun, P.; van Driel, T.; Vorberger, J.; Kraus, D.

We have investigated the high-pressure behavior of polyethylene by probing dynamically shock-compressed samples with x-ray diffraction. At high pressures, comparable to those present inside icy giant planets (Uranus, Neptune), shock-compressed polyethylene (CH2) retains a crystal structure, from which we infer the presence of significant covalent bonding. This finding appears to contrast with recent results from shock-compressed polystyrene (CH), which demonstrated demixing and recrystallization into a diamond lattice, implying the breaking of the original chemical bonds. As such chemical processes have significant implication for the structure and energy balance within ice giants, our results highlight the need for a deeper understanding of the chemistry of high pressure hydrocarbons, and underline the importance of better constraining the temperature profiles inside such planets.

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