1
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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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2
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Wang J, Gao H, Han Y, Ding C, Pan S, Wang Y, Jia Q, Wang HT, Xing D, Sun J. MAGUS: machine learning and graph theory assisted universal structure searcher. Natl Sci Rev 2023; 10:nwad128. [PMID: 37332628 PMCID: PMC10275355 DOI: 10.1093/nsr/nwad128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 03/30/2023] [Accepted: 04/28/2023] [Indexed: 06/20/2023] Open
Abstract
Crystal structure predictions based on first-principles calculations have gained great success in materials science and solid state physics. However, the remaining challenges still limit their applications in systems with a large number of atoms, especially the complexity of conformational space and the cost of local optimizations for big systems. Here, we introduce a crystal structure prediction method, MAGUS, based on the evolutionary algorithm, which addresses the above challenges with machine learning and graph theory. Techniques used in the program are summarized in detail and benchmark tests are provided. With intensive tests, we demonstrate that on-the-fly machine-learning potentials can be used to significantly reduce the number of expensive first-principles calculations, and the crystal decomposition based on graph theory can efficiently decrease the required configurations in order to find the target structures. We also summarized the representative applications of this method on several research topics, including unexpected compounds in the interior of planets and their exotic states at high pressure and high temperature (superionic, plastic, partially diffusive state, etc.); new functional materials (superhard, high-energy-density, superconducting, photoelectric materials), etc. These successful applications demonstrated that MAGUS code can help to accelerate the discovery of interesting materials and phenomena, as well as the significant value of crystal structure predictions in general.
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Affiliation(s)
| | | | | | - Chi Ding
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Shuning Pan
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yong Wang
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Qiuhan Jia
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Hui-Tian Wang
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Dingyu Xing
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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3
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Pan S, Huang T, Vazan A, Liang Z, Liu C, Wang J, Pickard CJ, Wang HT, Xing D, Sun J. Magnesium oxide-water compounds at megabar pressure and implications on planetary interiors. Nat Commun 2023; 14:1165. [PMID: 36859401 PMCID: PMC9977943 DOI: 10.1038/s41467-023-36802-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 02/15/2023] [Indexed: 03/03/2023] Open
Abstract
Magnesium Oxide (MgO) and water (H2O) are abundant in the interior of planets. Their properties, and in particular their interaction, significantly affect the planet interior structure and thermal evolution. Here, using crystal structure predictions and ab initio molecular dynamics simulations, we find that MgO and H2O can react again at ultrahigh pressure, although Mg(OH)2 decomposes at low pressure. The reemergent MgO-H2O compounds are: Mg2O3H2 above 400 GPa, MgO3H4 above 600 GPa, and MgO4H6 in the pressure range of 270-600 GPa. Importantly, MgO4H6 contains 57.3 wt % of water, which is a much higher water content than any reported hydrous mineral. Our results suggest that a substantial amount of water can be stored in MgO rock in the deep interiors of Earth to Neptune mass planets. Based on molecular dynamics simulations we show that these three compounds exhibit superionic behavior at the pressure-temperature conditions as in the interiors of Uranus and Neptune. Moreover, the water-rich compound MgO4H6 could be stable inside the early Earth and therefore may serve as a possible early Earth water reservoir. Our findings, in the poorly explored megabar pressure regime, provide constraints for interior and evolution models of wet planets in our solar system and beyond.
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Affiliation(s)
- Shuning Pan
- grid.41156.370000 0001 2314 964XNational Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093 Nanjing, China
| | - Tianheng Huang
- grid.41156.370000 0001 2314 964XNational Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093 Nanjing, China
| | - Allona Vazan
- grid.412512.10000 0004 0604 7424Astrophysics Research Center of the Open University (ARCO), The Open University of Israel, 4353701 Raanana, Israel
| | - Zhixin Liang
- grid.41156.370000 0001 2314 964XNational Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093 Nanjing, China
| | - Cong Liu
- grid.41156.370000 0001 2314 964XNational Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093 Nanjing, China
| | - Junjie Wang
- grid.41156.370000 0001 2314 964XNational Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093 Nanjing, China
| | - Chris J. Pickard
- grid.5335.00000000121885934Theory of Condensed Matter Group, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge, CB3 0HE UK ,grid.69566.3a0000 0001 2248 6943Advanced Institute for Materials Research, Tohoku University 2-1-1 Katahira, Aoba, Sendai, 980-8577 Japan
| | - Hui-Tian Wang
- grid.41156.370000 0001 2314 964XNational Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093 Nanjing, China
| | - Dingyu Xing
- grid.41156.370000 0001 2314 964XNational Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093 Nanjing, China
| | - Jian Sun
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
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4
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Li B, Liu H, Liu G, Chen K. First-principles study on high-pressure phases and compression properties of gold-bearing intermetallic compounds. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:464001. [PMID: 36063801 DOI: 10.1088/1361-648x/ac8f7b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 09/05/2022] [Indexed: 06/15/2023]
Abstract
Compared to elemental gold (Au), Au-based alloys have attracted wide attention for their economy and superior performance stemming from their distinctive physicochemical properties. The study of the structural characterization for alloy materials remains one of the fundamental issues associated with their future applications essentially. In this work, we theoretically explore some typical intermetallic compounds of Au-based alloys under high pressure, which has been an effective means to generate intriguing crystal configurations with unexpected behaviors. Ourab initiosimulations find thatFd-3m-AuRb,Fd-3m-AuBa, andFd-3m-AuLa become stable above ∼10 GPa, andPmmn-AuAl becomes stable above ∼20 GPa. Further investigations of their compression behaviors reveal that the bulk moduli of Au-based alloys can be greatly reduced by combining alkali and alkaline earth metals. The present results have unraveled the high-pressure phases of Au-bearing compounds and provide insights for exploring their important compressibility that is strongly relevant to the containing non-Au elements.
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Affiliation(s)
- Bingtan Li
- State Key Laboratory of Superhard Materials and International Center for Computational Method and Software, College of Physics, Jilin University, Changchun 130012, People's Republic of China
| | - Hanyu Liu
- State Key Laboratory of Superhard Materials and International Center for Computational Method and Software, College of Physics, Jilin University, Changchun 130012, People's Republic of China
- International Center of Future Science, Jilin University, Changchun 130012, People's Republic of China
| | - Guangtao Liu
- State Key Laboratory of Superhard Materials and International Center for Computational Method and Software, College of Physics, Jilin University, Changchun 130012, People's Republic of China
| | - Kaiguo Chen
- Department of Physics, National University of Defense Technology, Changsha 410073, People's Republic of China
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5
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Niu C, Zhang H, Zhang J, Zeng Z, Wang X. Ultralow Melting Temperature of High-Pressure Face-Centered Cubic Superionic Ice. J Phys Chem Lett 2022; 13:7448-7453. [PMID: 35930621 DOI: 10.1021/acs.jpclett.2c01814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Superionic ice with oxygen in a face-centered cubic (fcc) sublattice is ascribed to the origin of magnetic fields of Uranus and Neptune, since the melting temperature (Tm) of fcc-superionic ice is believed to be higher than the isentropes of ice giants. However, precisely measuring the fcc-superionic phase experimentally remains a difficult task. The majority of the systematic investigations of its Tm were performed using perfect oxygen fcc-sublattice computations, which could result in superheating and overestimation of Tm. On the basis of the ab initio molecular dynamics method and the model with H2O vacancy, we avoid superheating and obtain a much lower Tm than previous reports, indicating that fcc-superionic ice cannot exist in the interiors of Uranus and Neptune. Further simulations with the two-phase method justify the conclusion. The results suggest that superheating should be seriously treated when simulating the phase diagram of other hydrogen-related superionic states, which are widely used to understand the properties of ice giants, Earth, and Venus.
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Affiliation(s)
- Caoping Niu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Hanxing Zhang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Jie Zhang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Zhi Zeng
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Xianlong Wang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
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6
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Wei S, Zhang P, Liu H. High pressure nanoarchitectonics and metallization of barium chloride and barium bromide. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:294002. [PMID: 35477172 DOI: 10.1088/1361-648x/ac6b08] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 04/27/2022] [Indexed: 06/14/2023]
Abstract
As one of the most prototypicalAX2-type compounds, barium halide shared the cubic structure withFm-3msymmetry for BaCl2or orthorhombic structure withPnmasymmetry for BaBr2at ambient pressure. In this work, we explored the crystal structures of BaCl2and BaBr2under high pressure. We predicted a thermodynamically more favored structure with orthorhombicCmcmsymmetry for both BaCl2and BaBr2, at 74 and 47 GPa, respectively. Our simulations reveal that the metallic feature ofCmcmBaCl2andCmcmBaBr2under high pressure. The present results improve the understanding of high-pressure structures ofAX2compounds at extremely high-pressure conditions.
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Affiliation(s)
- Shubo Wei
- International Center for Computational Methods and Software and State Key Laboratory for Superhard Materials, College of Physics, Jilin University, Changchun 130012, People's Republic of China
| | - Peiyu Zhang
- International Center for Computational Methods and Software and State Key Laboratory for Superhard Materials, College of Physics, Jilin University, Changchun 130012, People's Republic of China
| | - Hanyu Liu
- International Center for Computational Methods and Software and State Key Laboratory for Superhard Materials, College of Physics, Jilin University, Changchun 130012, People's Republic of China
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7
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Gao H, Liu C, Shi J, Pan S, Huang T, Lu X, Wang HT, Xing D, Sun J. Superionic Silica-Water and Silica-Hydrogen Compounds in the Deep Interiors of Uranus and Neptune. PHYSICAL REVIEW LETTERS 2022; 128:035702. [PMID: 35119900 DOI: 10.1103/physrevlett.128.035702] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 12/03/2021] [Accepted: 12/24/2021] [Indexed: 06/14/2023]
Abstract
Silica, water, and hydrogen are known to be the major components of celestial bodies, and have significant influence on the formation and evolution of giant planets, such as Uranus and Neptune. Thus, it is of fundamental importance to investigate their states and possible reactions under the planetary conditions. Here, using advanced crystal structure searches and first-principles calculations in the Si-O-H system, we find that a silica-water compound (SiO_{2})_{2}(H_{2}O) and a silica-hydrogen compound SiO_{2}H_{2} can exist under high pressures above 450 and 650 GPa, respectively. Further simulations reveal that, at high pressure and high temperature conditions corresponding to the interiors of Uranus and Neptune, these compounds exhibit superionic behavior, in which protons diffuse freely like liquid while the silicon and oxygen framework is fixed as solid. Therefore, these superionic silica-water and silica-hydrogen compounds could be regarded as important components of the deep mantle or core of giants, which also provides an alternative origin for their anomalous magnetic fields. These unexpected physical and chemical properties of the most common natural materials at high pressure offer key clues to understand some abstruse issues including demixing and erosion of the core in giant planets, and shed light on building reliable models for solar giants and exoplanets.
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Affiliation(s)
- Hao Gao
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Cong Liu
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jiuyang Shi
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Shuning Pan
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Tianheng Huang
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xiancai Lu
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China
| | - Hui-Tian Wang
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Dingyu Xing
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jian Sun
- National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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8
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Wei S, Liu H. High-Pressure Structures and Superconductivity of Barium Iodide. MATERIALS (BASEL, SWITZERLAND) 2022; 15:522. [PMID: 35057239 PMCID: PMC8778895 DOI: 10.3390/ma15020522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 02/01/2023]
Abstract
Generally, pressure is a useful tool to modify the behavior of physical properties of materials due to the change in distance between atoms or molecules in the lattice. Barium iodide (BaI2), as one of the simplest and most prototypical iodine compounds, has substantial high pressure investigation value. In this work, we explored the crystal structures of BaI2 at a wide pressure range of 0-200 GPa using a global structure search methodology. A thermodynamical structure with tetragonal I4/mmm symmetry of BaI2 was predicted to be stable at 17.1 GPa. Further electronic calculations indicated that I4/mmm BaI2 exhibits the metallic feature via an indirect band gap closure under moderate pressure. We also found that the superconductivity of BaI2 at 30 GPa is much lower than that of CsI at 180 GPa based on our electron-phonon coupling simulations. Our current simulations provide a step toward the further understanding of the high-pressure behavior of iodine compounds at extreme conditions.
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Affiliation(s)
- Shubo Wei
- State Key Laboratory for Superhard Materials, College of Physics, Jilin University, Changchun 130012, China;
- International Center for Computational Methods and Software, College of Physics, Jilin University, Changchun 130012, China
| | - Hanyu Liu
- State Key Laboratory for Superhard Materials, College of Physics, Jilin University, Changchun 130012, China;
- International Center for Computational Methods and Software, College of Physics, Jilin University, Changchun 130012, China
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9
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Liang T, Zhang Z, Yu H, Cui T, Feng X, Pickard CJ, Duan D, Redfern SAT. Pressure-Induced Superionicity of H - in Hypervalent Sodium Silicon Hydrides. J Phys Chem Lett 2021; 12:7166-7172. [PMID: 34297555 DOI: 10.1021/acs.jpclett.1c01809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Superionic states simultaneously exhibit properties of a fluid and a solid. Proton (H+) superionicity in ice, H3O, He-H2O, and He-NH3 compounds is well-studied. However, hydride (H-) superionicity in H-rich compounds is rare, being associated with instability and strongly reducing conditions. Silicon, sodium, and hydrogen are abundant elements in many astrophysical bodies. Here, we use first-principles calculations to show that, at high pressure, Na, Si, and H can form several hypervalent compounds. A previously unreported superionic state of Na2SiH6 results from unconstrained H- in the hypervalent [SiH6]2- unit. Na2SiH6 is dynamically stable at low pressure (3 GPa), becoming superionic at 5 GPa, and re-entering solid/fluid states at about 25 GPa. Our observation of H- transport opens up a new field of H- conductors. It also has implications for the formation of conducting layers at depth in exotic carbon exoplanets, potentially enhancing the habitability of such planets.
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Affiliation(s)
- Tianxiao Liang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
| | - Zihan Zhang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
| | - Hongyu Yu
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
| | - Tian Cui
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- Institute of High Pressure Physics, School of Physical Science and Technology, Ningbo University, Ningbo 315211, China
| | - Xiaolei Feng
- Institute for Disaster Management and Reconstruction, Sichuan University - the Hong Kong Polytechnic University, Chengdu 610207, China
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, United Kingdom
| | - Chris J Pickard
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
- Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
| | - Defang Duan
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
| | - Simon A T Redfern
- Asian School of the Environment, Nanyang Technological University, Singapore 639798
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10
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Li X, Lowe A, Conway L, Miao M, Hermann A. First principles study of dense and metallic nitric sulfur hydrides. Commun Chem 2021; 4:83. [PMID: 36697602 PMCID: PMC9814481 DOI: 10.1038/s42004-021-00517-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 04/30/2021] [Indexed: 02/04/2023] Open
Abstract
Studies of molecular mixtures containing hydrogen sulfide (H2S) could open up new routes towards hydrogen-rich high-temperature superconductors under pressure. H2S and ammonia (NH3) form hydrogen-bonded molecular mixtures at ambient conditions, but their phase behavior and propensity towards mixing under pressure is not well understood. Here, we show stable phases in the H2S-NH3 system under extreme pressure conditions to 4 Mbar from first-principles crystal structure prediction methods. We identify four stable compositions, two of which, (H2S) (NH3) and (H2S) (NH3)4, are stable in a sequence of structures to the Mbar regime. A re-entrant stabilization of (H2S) (NH3)4 above 300 GPa is driven by a marked reversal of sulfur-hydrogen chemistry. Several stable phases exhibit metallic character. Electron-phonon coupling calculations predict superconducting temperatures up to 50 K, in the Cmma phase of (H2S) (NH3) at 150 GPa. The present findings shed light on how sulfur hydride bonding and superconductivity are affected in molecular mixtures. They also suggest a reservoir for hydrogen sulfide in the upper mantle regions of icy planets in a potentially metallic mixture, which could have implications for their magnetic field formation.
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Affiliation(s)
- Xiaofeng Li
- grid.440830.b0000 0004 1793 4563College of Physics and Electronic Information, Luoyang Normal University, Luoyang, China ,grid.4305.20000 0004 1936 7988Centre for Science at Extreme Conditions and SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, UK
| | - Angus Lowe
- grid.4305.20000 0004 1936 7988Centre for Science at Extreme Conditions and SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, UK
| | - Lewis Conway
- grid.4305.20000 0004 1936 7988Centre for Science at Extreme Conditions and SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, UK
| | - Maosheng Miao
- grid.253563.40000 0001 0657 9381Department of Chemistry & Biochemistry, California State University, Northridge, CA USA ,grid.133342.40000 0004 1936 9676Department of Earth Science, University of California Santa Barbara, CA, USA
| | - Andreas Hermann
- grid.4305.20000 0004 1936 7988Centre for Science at Extreme Conditions and SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, UK
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11
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Conway LJ, Pickard CJ, Hermann A. Rules of formation of H-C-N-O compounds at high pressure and the fates of planetary ices. Proc Natl Acad Sci U S A 2021; 118:e2026360118. [PMID: 33931549 PMCID: PMC8126778 DOI: 10.1073/pnas.2026360118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The solar system's outer planets, and many of their moons, are dominated by matter from the H-C-N-O chemical space, based on solar system abundances of hydrogen and the planetary ices [Formula: see text]O, [Formula: see text], and [Formula: see text] In the planetary interiors, these ices will experience extreme pressure conditions, around 5 Mbar at the Neptune mantle-core boundary, and it is expected that they undergo phase transitions, decompose, and form entirely new compounds. While temperature will dictate the formation of compounds, ground-state density functional theory allows us to probe the chemical effects resulting from pressure alone. These structural developments in turn determine the planets' interior structures, thermal evolution, and magnetic field generation, among others. Despite its importance, the H-C-N-O system has not been surveyed systematically to explore which compounds emerge at high-pressure conditions, and what governs their stability. Here, we report on and analyze an unbiased crystal structure search among H-C-N-O compounds between 1 and 5 Mbar. We demonstrate that simple chemical rules drive stability in this composition space, which explains why the simplest possible quaternary mixture HCNO-isoelectronic to diamond-emerges as a stable compound and discuss dominant decomposition products of planetary ice mixtures.
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Affiliation(s)
- Lewis J Conway
- Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
- School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - Chris J Pickard
- Department of Materials Science & Metallurgy, University of Cambridge, Cambridge CB3 0FS, United Kingdom
- Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Andreas Hermann
- Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom;
- School of Physics and Astronomy, The University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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12
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Shi J, Cui W, Hao J, Xu M, Wang X, Li Y. Formation of ammonia-helium compounds at high pressure. Nat Commun 2020; 11:3164. [PMID: 32572021 PMCID: PMC7308345 DOI: 10.1038/s41467-020-16835-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 05/28/2020] [Indexed: 11/09/2022] Open
Abstract
Uranus and Neptune are generally assumed to have helium only in their gaseous atmospheres. Here, we report the possibility of helium being fixed in the upper mantles of these planets in the form of NH3-He compounds. Structure predictions reveal two energetically stable NH3-He compounds with stoichiometries (NH3)2He and NH3He at high pressures. At low temperatures, (NH3)2He is ionic with NH3 molecules partially dissociating into (NH2)- and (NH4)+ ions. Simulations show that (NH3)2He transforms into intermediate phase at 100 GPa and 1000 K with H atoms slightly vibrate around N atoms, and then to a superionic phase at ~2000 K with H and He exhibiting liquid behavior within the fixed N sublattice. Finally, (NH3)2He becomes a fluid phase at temperatures of 3000 K. The stability of (NH3)2He at high pressure and temperature could contribute to update models of the interiors of Uranus and Neptune.
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Affiliation(s)
- Jingming Shi
- Laboratory of Quantum Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, 221116, China
| | - Wenwen Cui
- Laboratory of Quantum Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, 221116, China
| | - Jian Hao
- Laboratory of Quantum Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, 221116, China.,Jiangsu Key Laboratory of Advanced Laser Materials and Devices, Jiangsu Normal University, Xuzhou, 221116, China
| | - Meiling Xu
- Laboratory of Quantum Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, 221116, China
| | - Xianlong Wang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, China.
| | - Yinwei Li
- Laboratory of Quantum Materials Design and Application, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, 221116, China.
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