List of publications

Physical Review B, 114, 094103, (2026) [doi: 10.1103/kxnf-6c5y]

Observation of body-centered cubic iron above 200 gigapascals

Z. Konôpková, E. Edmund, O. B. Ball, A. Dewaele, H. Ginestet, R. J. Husband, N. Jaisle, C. Strohm, M. S. Anae, D. Antonangeli, K. Appel, M. Baron, S. Boccato, K. Buakor, J. Chantel, H. Cynn, A. P. Dwivedi, L. Ehm, K. Glazyrin, H. Graafsma, E. Koemets, T. Laurus, H. Marquardt, B. Massani, J. D. McHardy, M. I. McMahon, V. Prakapenka, J. Sztuk-Dambietz, M. Tang, T. Xie, Z. Younes, U. Zastrau, A. F. Goncharov, C. Prescher, R. S. McWilliams, G. Morard & S. Merkel

The crystallographic structure of iron under extreme conditions is a key benchmark for state-of-the-art experimental and computational methods. Moreover, it plays a crucial role in our understanding of planetary cores, as it strongly influences the interpretation of observational data and, consequently, our knowledge of their internal structure and dynamics. However, even the crystal structure of pure solid iron under Earth's core conditions remains uncertain, with the commonly expected hexagonal close-packed phase being energetically competitive with several cubic structures. In this study, iron was compressed in a diamond anvil cell to pressures exceeding 200 GPa and dynamically probed near its melting point using MHz-frequency x-ray pulses from the European X-ray Free-Electron Laser. In the pressure range between 120 and 160 GPa, the high temporal resolution of the structural snapshots at elevated temperatures revealed the face-centered cubic phase, extending its observed stability to higher pressures than previously reported. Brief appearances of intermediate or disordered phases, including body-centered cubic (bcc) and stacking-faulted structures, were also observed. Above 230 GPa, new diffraction reflections emerged at high temperatures and are interpreted as evidence for the nucleation of a previously unreported phase, which subsequently evolved into a powderlike diffraction pattern characteristic of the bcc structure. The unprecedented time resolution of the structural data acquired during rapid heating and cooling cycles provides insights into the kinetics and mechanisms of phase transformations in iron at these extreme pressures.

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