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Roy AJ, Bergermann A, Bethkenhagen M, Redmer R. Mixture of hydrogen and methane under planetary interior conditions. Phys Chem Chem Phys 2024; 26:14374-14383. [PMID: 38712595 DOI: 10.1039/d4cp00058g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
We employ first-principles molecular dynamics simulations to provide equation-of-state data, pair distribution functions (PDFs), diffusion coefficients, and band gaps of a mixture of hydrogen and methane under planetary interior conditions as relevant for Uranus, Neptune, and similar icy exoplanets. We test the linear mixing approximation, which is fulfilled within a few percent for the chosen P-T conditions. Evaluation of the PDFs reveals that methane molecules dissociate into carbon clusters and free hydrogen atoms at temperatures greater than 3000 K. At high temperatures, the clusters are found to be short-lived. Furthermore, we calculate the electrical conductivity from which we derive the non-metal-to-metal transition region of the mixture. We also calculate the electrical conductivity along the P-T profile of Uranus [N. Nettelmann et al., Planet. Space Sci., 2013, 77, 143-151] and observe the transition of the mixture from a molecular to an atomic fluid as a function of the radius of the planet. The density and temperature ranges chosen in our study can be achieved using dynamic shock compression experiments and seek to aid such future experiments. Our work also provides a relevant data set for a better understanding of the interior, evolution, luminosity, and magnetic field of the ice giants in our solar system and beyond.
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Affiliation(s)
- Argha Jyoti Roy
- Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
| | - Armin Bergermann
- Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
| | - Mandy Bethkenhagen
- LULI, CNRS, CEA, Sorbonne Université, École Polytechnique - Institut Polytechnique de Paris, 91128 Palaiseau, France.
| | - Ronald Redmer
- Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
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Koller TJ, Jin S, Krol V, Ambach SJ, Ranieri U, Khandarkhaeva S, Spender J, McWilliams S, Trybel F, Giordano N, Poreba T, Mezouar M, Kuang X, Lu C, Dubrovinsky L, Dubrovinskaia N, Hermann A, Schnick W, Laniel D. Simple Molecules under High-Pressure and High-Temperature Conditions: Synthesis and Characterization of α- and β-C(NH) 2 with Fully sp 3 -Hybridized Carbon. Angew Chem Int Ed Engl 2024; 63:e202318214. [PMID: 38100520 DOI: 10.1002/anie.202318214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/14/2023] [Accepted: 12/15/2023] [Indexed: 12/17/2023]
Abstract
The elements hydrogen, carbon, and nitrogen are among the most abundant in the solar system. Still, little is known about the ternary compounds these elements can form under the high-pressure and high-temperature conditions found in the outer planets' interiors. These materials are also of significant research interest since they are predicted to feature many desirable properties such as high thermal conductivity and hardness due to strong covalent bonding networks. In this study, the high-pressure high-temperature reaction behavior of malononitrile H2 C(CN)2 , dicyandiamide (H2 N)2 C=NCN, and melamine (C3 N3 )(NH2 )3 was investigated in laser-heated diamond anvil cells. Two previously unknown compounds, namely α-C(NH)2 and β-C(NH)2 , have been synthesized and found to have fully sp3 -hybridized carbon atoms. α-C(NH)2 crystallizes in a distorted β-cristobalite structure, while β-C(NH)2 is built from previously unknown imide-bridged 2,4,6,8,9,10-hexaazaadamantane units, which form two independent interpenetrating diamond-like networks. Their stability domains and compressibility were studied, for which supporting density functional theory calculations were performed.
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Affiliation(s)
- Thaddäus J Koller
- Department of Chemistry, University of Munich (LMU), Butenandtstrasse 5-13, 81377, Munich, Germany
| | - Siyu Jin
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, 610065, China
| | - Viktoria Krol
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Sebastian J Ambach
- Department of Chemistry, University of Munich (LMU), Butenandtstrasse 5-13, 81377, Munich, Germany
| | - Umbertoluca Ranieri
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Saiana Khandarkhaeva
- Bavarian Research Institute of Experimental Geochemistry and Geophysics (BGI), University of Bayreuth, 95440, Bayreuth, Germany
| | - James Spender
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Stewart McWilliams
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Florian Trybel
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183, Linköping, Sweden
| | - Nico Giordano
- P02.2 Extreme Conditions Beamline, Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607, Hamburg, Germany
| | - Tomasz Poreba
- ID27 High Pressure Beamline, European Synchrotron Radiation Facility (ESRF), 71 avenue des Martyrs, 38000, Grenoble, France
| | - Mohamed Mezouar
- ID27 High Pressure Beamline, European Synchrotron Radiation Facility (ESRF), 71 avenue des Martyrs, 38000, Grenoble, France
| | - Xiaoyu Kuang
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, 610065, China
| | - Cheng Lu
- School of Mathematics and Physics, China University of Geosciences (Wuhan), Wuhan, 430074, China
| | - Leonid Dubrovinsky
- Bavarian Research Institute of Experimental Geochemistry and Geophysics (BGI), University of Bayreuth, 95440, Bayreuth, Germany
| | - Natalia Dubrovinskaia
- Bavarian Research Institute of Experimental Geochemistry and Geophysics (BGI), University of Bayreuth, 95440, Bayreuth, Germany
| | - Andreas Hermann
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Wolfgang Schnick
- Department of Chemistry, University of Munich (LMU), Butenandtstrasse 5-13, 81377, Munich, Germany
| | - Dominique Laniel
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, UK
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de Villa K, González-Cataldo F, Militzer B. Double superionicity in icy compounds at planetary interior conditions. Nat Commun 2023; 14:7580. [PMID: 37990010 PMCID: PMC10663582 DOI: 10.1038/s41467-023-42958-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 10/27/2023] [Indexed: 11/23/2023] Open
Abstract
The elements hydrogen, carbon, nitrogen and oxygen are assumed to comprise the bulk of the interiors of the ice giant planets Uranus, Neptune, and sub-Neptune exoplanets. The details of their interior structures have remained largely unknown because it is not understood how the compounds H2O, NH3 and CH4 behave and react once they have been accreted and exposed to high pressures and temperatures. Here we study thirteen H-C-N-O compounds with ab initio computer simulations and demonstrate that they assume a superionic state at elevated temperatures, in which the hydrogen ions diffuse through a stable sublattice that is provided by the larger nuclei. At yet higher temperatures, four of the thirteen compounds undergo a second transition to a novel doubly superionic state, in which the smallest of the heavy nuclei diffuse simultaneously with hydrogen ions through the remaining sublattice. Since this transition and the melting transition at yet higher temperatures are both of first order, this may introduce additional layers in the mantle of ice giant planets and alter their convective patterns.
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Affiliation(s)
- Kyla de Villa
- Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA.
| | - Felipe González-Cataldo
- Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA
| | - Burkhard Militzer
- Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA
- Department of Astronomy, University of California, Berkeley, CA, 94720, USA
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Abstract
SignificanceOver the years, many unusual chemical phenomena have been discovered at high pressures, yet our understanding of them is still very fragmentary. Our paper addresses this from the fundamental level by exploring the key chemical properties of atoms-electronegativity and chemical hardness-as a function of pressure. We have made an appropriate modification to the definition of Mulliken electronegativity to extend its applicability to high pressures. The change in atomic properties, which we observe, allows us to provide a unified framework explaining (and predicting) many chemical phenomena and the altered behavior of many elements under pressure.
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