| Autor: |
Ranieri U; Dipartimento di Fisica, Sapienza Università di Roma, 00185 Roma, Italy.; Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, EH9 3FD Edinburgh, United Kingdom., Di Cataldo S; Dipartimento di Fisica, Sapienza Università di Roma, 00185 Roma, Italy.; Institut für Festkörperphysik, Technische Universität Wien, 1040 Wien, Austria., Rescigno M; Dipartimento di Fisica, Sapienza Università di Roma, 00185 Roma, Italy.; Laboratory of Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland., Monacelli L; Theory and Simulation of Materials, and National Centre for Computational Design and Discovery of Novel Materials, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland., Gaal R; Laboratory of Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland., Santoro M; Consiglio Nazionale delle Ricerche, Istituto Nazionale di Ottica, CNR-INO, Sesto Fiorentino, 50019, Italy.; European Laboratory for Nonlinear Spectroscopy, LENS, Sesto Fiorentino (FI), 50019, Italy., Andriambariarijaona L; Sorbonne Université, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, 75252 Paris, France., Parisiades P; Sorbonne Université, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, 75252 Paris, France., De Michele C; Dipartimento di Fisica, Sapienza Università di Roma, 00185 Roma, Italy., Bove LE; Dipartimento di Fisica, Sapienza Università di Roma, 00185 Roma, Italy.; Laboratory of Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.; Sorbonne Université, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, 75252 Paris, France. |
| Abstrakt: |
Hydrogen hydrates are among the basic constituents of our solar system's outer planets, some of their moons, as well Neptune-like exo-planets. The details of their high-pressure phases and their thermodynamic conditions of formation and stability are fundamental information for establishing the presence of hydrogen hydrates in the interior of those celestial bodies, for example, against the presence of the pure components (water ice and molecular hydrogen). Here, we report a synthesis path and experimental observation, by X-ray diffraction and Raman spectroscopy measurements, of the most H[Formula: see text]-dense phase of hydrogen hydrate so far reported, namely the compound 3 (or C[Formula: see text]). The detailed characterisation of this hydrogen-filled ice, based on the crystal structure of cubic ice I (ice I[Formula: see text]), is performed by comparing the experimental observations with first-principles calculations based on density functional theory and the stochastic self-consistent harmonic approximation. We observe that the extreme (up to 90 GPa and likely beyond) pressure stability of this hydrate phase is due to the close-packed geometry of the hydrogen molecules caged in the ice I[Formula: see text] skeleton. |
