Greifswald 2024 – scientific programme

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P: Fachverband Plasmaphysik

P 4: Astrophysical Plasmas/Laser Plasmas

P 4.6: Talk

Monday, February 26, 2024, 15:30–15:45, WW 1: HS

Nonmetal-to-metal transition in dense fluid nitrogen at high pressure — Armin Bergermann and •Ronald Redmer — Univ. Rostock, Institut für Physik, A.-Einstein-Str. 23, 18059 Rostock

The high-pressure phase diagram of solid nitrogen is extremely rich: 12 molecular phases, two nonmolecular phases, and an amorphous one have been reported so far [1]. Recent molecular dynamics (MD) simulations on dense fluid nitrogen using density functional theory (DFT) predict a first-order liquid-liquid phase transition (LL-PT) at about a megabar, see e.g. [2]. Static experiments using diamond anvil cells as well as dynamic shock-wave experiments have been applied to access the corresponding region.

We calculate the electrical conductivity and the equation of state of dense fluid nitrogen for high pressures up to several megabars by using DFT-MD simulations [3]. We determine the instability region of the first-order LL-PT which results from an abrupt dissociation of nitrogen molecules. This transition is accompanied by a nonmetal-to-metal transition (metallization) of the fluid and corresponding structural changes from a molecular to a polymeric phase. We compare our data with earlier theoretical results and available experiments.

[1] R. Turnbull et al., Nat. Commun. 9, 4717 (2018) [2] B. Boates, S. A. Bonev, Phys. Rev. Lett. 102, 015701 (2009). [3] A. Bergermann, R. Redmer, Phys. Rev. B 108, 085101 (2023)

Keywords: ab initio simulations; dense fluid nitrogen; equaton of state; nonmetal-to-metal transition; high-pressure phase diagram