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Ma L, Wang K, Xie Y, Yang X, Wang Y, Zhou M, Liu H, Yu X, Zhao Y, Wang H, Liu G, Ma Y. High-Temperature Superconducting Phase in Clathrate Calcium Hydride CaH_{6} up to 215 K at a Pressure of 172 GPa. PHYSICAL REVIEW LETTERS 2022; 128:167001. [PMID: 35522494 DOI: 10.1103/physrevlett.128.167001] [Citation(s) in RCA: 68] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 01/18/2022] [Accepted: 03/09/2022] [Indexed: 05/25/2023]
Abstract
The recent discovery of superconductive rare earth and actinide superhydrides has ushered in a new era of superconductivity research at high pressures. This distinct type of clathrate metal hydrides was first proposed for alkaline-earth-metal hydride CaH_{6} that, however, has long eluded experimental synthesis, impeding an understanding of pertinent physics. Here, we report successful synthesis of CaH_{6} and its measured superconducting critical temperature T_{c} of 215 K at 172 GPa, which is evidenced by a sharp drop of resistivity to zero and a characteristic decrease of T_{c} under a magnetic field up to 9 T. An estimate based on the Werthamer-Helfand-Hohenberg model gives a giant zero-temperature upper critical magnetic field of 203 T. These remarkable benchmark superconducting properties place CaH_{6} among the most outstanding high-T_{c} superhydrides, marking it as the hitherto only clathrate metal hydride outside the family of rare earth and actinide hydrides. This exceptional case raises great prospects of expanding the extraordinary class of high-T_{c} superhydrides to a broader variety of compounds that possess more diverse material features and physics characteristics.
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Affiliation(s)
- Liang Ma
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
- International Center of Future Science, Jilin University, Changchun 130012, China
| | - Kui Wang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
| | - Yu Xie
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Jilin University, Changchun 130012, China
| | - Xin Yang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
| | - Yingying Wang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
| | - Mi Zhou
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
| | - Hanyu Liu
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
- International Center of Future Science, Jilin University, Changchun 130012, China
- State Key Laboratory of Superhard Materials and Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012, China
| | - Xiaohui Yu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yongsheng Zhao
- Deutsches Elektronen-Synchrotron DESY, Hamburg 22607, Germany
| | - Hongbo Wang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
| | - Guangtao Liu
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
| | - Yanming Ma
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
- International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China
- International Center of Future Science, Jilin University, Changchun 130012, China
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Zhu SC, Huang ZB, Hu Q, Xu L. Pressure tuned incommensurability and guest structure transition in compressed scandium from machine learning atomic simulation. Phys Chem Chem Phys 2022; 24:7007-7013. [PMID: 35254347 DOI: 10.1039/d1cp05803g] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Scandium (Sc) is the lightest non-main-group element and transforms to a host-guest (H-G) incommensurate structure under gigapascal (GPa) pressures. While the host structure is stable over a wide pressure range, the guest structure may exist in multiple forms, featuring different incommensurate ratios, and mixing up to generate long-range "disordered" guest structures. Here, we employed the recently developed global neural network (g-NN) potential and the stochastic surface walking (SSW) global optimization algorithm to explore the global potential energy surface of Sc under various pressures. We probe the global minima structure in a system made of hundreds of atoms and revealed that the solid-phase transition between Sc-I and H-G Sc-II phases is fully reconstructive in nature. Above 62.5 GPa, the pressure will further destabilize the face-centered tetragonal (fct, Sc-IIa) guest structure to a body-centered tetragonal phase (bct, Sc-IIb), while sustaining the host structure. The structural transition mechanism of this work will shed light on the nature of the complex H-G structural modifications in compressed metals.
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Affiliation(s)
- Sheng-Cai Zhu
- School of Materials, Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China.
| | - Zhen-Bo Huang
- School of Materials, Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China.
| | - Qingyang Hu
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, P. R. China.,CAS Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, P. R. China
| | - Liang Xu
- National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
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Abstract
Various single elements form incommensurate crystal structures under pressure, where a zeolite-type "host" sublattice surrounds a "guest" sublattice comprising 1D chains of atoms. On "chain melting," diffraction peaks from the guest sublattice vanish, while those from the host remain. Diffusion of the guest atoms is expected to be confined to the channels in the host sublattice, which suggests 1D melting. Here, we present atomistic simulations of potassium to investigate this phenomenon and demonstrate that the chain-melted phase has no long-ranged order either along or between the chains. This 3D disorder provides the extensive entropy necessary to make the chain melt a true thermodynamic phase of matter, yet with the unique property that diffusion remains confined to 1D only. Calculations necessitated the development of an interatomic forcefield using machine learning, which we show fully reproduces potassium's phase diagram, including the chain-melted state and 14 known phase transitions.
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Li N, Manoun B, Tang L, Ke F, Liu F, Dong H, Lazor P, Yang W. Pressure-Induced Structural and Electronic Transition in Sr2ZnWO6 Double Perovskite. Inorg Chem 2016; 55:6770-5. [PMID: 27308777 DOI: 10.1021/acs.inorgchem.6b01091] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High-pressure structural and electrical properties of Sr2ZnWO6 double perovskite were investigated using in situ angle-dispersive synchrotron X-ray diffraction (XRD), Raman, and alternating current (AC) impedance spectroscopy. A structural transition from monoclinic (P21/n) to triclinic (P1̅) phase around 9 GPa was observed due to the pressure-induced distortion of (W, Zn)O6 octahedron. In situ high-pressure Raman spectroscopy showed the increasing interaction among O-W-O in WO6 octahedron with pressure and a transition pressure consistent with the XRD results. From the AC impedance spectroscopy measurements, the resistivity increased steeply by ∼1 order of magnitude around 11 GPa, indicating an electronic transition accompanying the symmetry change. The increase in the interaction among O-W-O enhances the attraction of O(2-) electrons toward W(6+), thus increasing the covalence, which in turn lowers the charge transfer energy between O(2-) and W(6+) and induces the resistivity increase under high pressure.
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Affiliation(s)
- Nana Li
- Center for High Pressure Science and Technology Advanced Research , Shanghai 201203, China
| | - Bouchaib Manoun
- Universite Hassan 1er , Laboratoire des Sciences des Matériaux, des Milieux et de la modélisation (LS3M), 25000, Khouribga, Morocco
| | - Lingyun Tang
- Center for High Pressure Science and Technology Advanced Research , Shanghai 201203, China.,High Pressure Synergetic Consortium, Geophysical Laboratory, Carnegie Institution of Washington , Argonne, Illinois 60439, United States
| | - Feng Ke
- Center for High Pressure Science and Technology Advanced Research , Shanghai 201203, China
| | - Fengliang Liu
- Center for High Pressure Science and Technology Advanced Research , Shanghai 201203, China.,The state Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University , Shanghai 200433, China
| | - Haini Dong
- Center for High Pressure Science and Technology Advanced Research , Shanghai 201203, China.,Key Laboratory of High-temperature and High-pressure Study of the Earth's Interior, Institute of Geochemistry, Chinese Academy of Sciences , Guizhou 550081, China
| | - Peter Lazor
- Department of Earth Sciences, Uppsala University , SE-752 36 Uppsala, Sweden
| | - Wenge Yang
- Center for High Pressure Science and Technology Advanced Research , Shanghai 201203, China.,High Pressure Synergetic Consortium, Geophysical Laboratory, Carnegie Institution of Washington , Argonne, Illinois 60439, United States
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Wang L, Huang X, Li D, Huang Y, Bao K, Li F, Wu G, Liu B, Cui T. Pressure-induced structural transformation of CaC2. J Chem Phys 2016; 144:194506. [DOI: 10.1063/1.4948705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Lu Wang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Xiaoli Huang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Da Li
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Yanping Huang
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Kuo Bao
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Fangfei Li
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Gang Wu
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Bingbing Liu
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
| | - Tian Cui
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People’s Republic of China
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Investigation of exotic stable calcium carbides using theory and experiment. Nat Commun 2015; 6:6974. [PMID: 25959292 PMCID: PMC4432597 DOI: 10.1038/ncomms7974] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 03/18/2015] [Indexed: 11/23/2022] Open
Abstract
It is well known that pressure causes profound changes in the properties of atoms and chemical bonding, leading to the formation of many unusual materials. Here we systematically explore all stable calcium carbides at pressures from ambient to 100 GPa using variable-composition evolutionary structure predictions using the USPEX code. We find that Ca5C2, Ca2C, Ca3C2, CaC, Ca2C3 and CaC2 have stability fields on the phase diagram. Among these, Ca2C and Ca2C3 are successfully synthesized for the first time via high-pressure experiments with excellent structural correspondence to theoretical predictions. Of particular significance is the base-centred monoclinic phase (space group C2/m) of Ca2C, a quasi-two-dimensional metal with layers of negatively charged calcium atoms, and the primitive monoclinic phase (space group P21/c) of CaC with zigzag C4 groups. Interestingly, strong interstitial charge localization is found in the structure of R-3m-Ca5C2 with semi-metallic behaviour. Pressure causes profound changes in the properties of atoms and chemical bonding leading to unusual materials. Here, the authors investigate the Ca-C system and find that it becomes increasingly complex and develops a multitude of phases with various compositions and new structures at higher pressures.
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Rio BGD, González LE. Orbital free ab initio simulations of liquid alkaline earth metals: from pseudopotential construction to structural and dynamic properties. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:465102. [PMID: 25347355 DOI: 10.1088/0953-8984/26/46/465102] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have performed a comprehensive study of the properties of liquid Be, Ca and Ba, through the use of orbital free ab initio simulations. To this end we have developed a force-matching method to construct the necessary local pseudopotentials from standard ab initio calculations. The structural magnitudes are analyzed, including the average and local structures and the dynamic properties are studied. We find several common features, like an asymmetric second peak in the structure factor, a large amount of local structures with five-fold symmetry, a quasi-universal behaviour of the single-particle dynamic properties and a large degree of positive dispersion in the propagation of collective density fluctuations, whose damping is dictated by slow thermal relaxations and fast viscoelastic ones. Some peculiarities in the dynamic properties are however observed, like a very high sound velocity and a large violation of the Stokes-Einstein relation for Be, or an extremely high positive dispersion and a large slope in the dispersion relation of shear waves at the onset of the wavevector region where they are supported for Ba.
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Affiliation(s)
- Beatriz G del Rio
- Departamento de Física Teórica, Universidad de Valladolid, C/Real De Burgos, S/N 47011 Valladolid, Spain
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McMahon MI. High-pressure X-ray science on the ultimate storage ring. JOURNAL OF SYNCHROTRON RADIATION 2014; 21:1077-1083. [PMID: 25177996 DOI: 10.1107/s1600577514012855] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 06/02/2014] [Indexed: 06/03/2023]
Abstract
The advent of the ESRF, APS and SPring-8 third-generation synchrotron sources in the mid-1990s heralded a golden age of high-pressure X-ray science. The high-energy monochromatic micro-focused X-ray beams from these storage rings, combined with the new high-pressure diffraction and spectroscopy techniques developed in the late 1980s, meant that researchers were immediately able to make detailed structural studies at pressures comparable with those at the centre of the Earth, studies that were simply not possible only five years previously. And new techniques, such as X-ray inelastic scattering and X-ray nuclear scattering, became possible at high pressure for the first time, providing wholly-new insight into the behaviour of materials at high densities. The arrival of new diffraction-limited storage rings, with their much greater brightness, and ability to achieve focal-spot diameters for high-energy X-ray beams of below 1 µm, offers the possibility of a new generation of high-pressure science, both extending the scope of what is already possible, and also opening ways to wholly-new areas of investigation.
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Affiliation(s)
- Malcolm I McMahon
- SUPA, School of Physics and Astronomy, and Centre for Science at Extreme Conditions, The University of Edinburgh, Edinburgh, UK
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Degtyareva VF. Structural simplicity and complexity of compressed calcium: electronic origin. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2014; 70:423-428. [PMID: 24892588 DOI: 10.1107/s2052520614002704] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 02/05/2014] [Indexed: 06/03/2023]
Abstract
A simple cubic structure with one atom in the unit cell found in compressed calcium is counterintuitive to the traditional view of a tendency towards densely packed structures with an increase in pressure. To understand this unusual transformation it is necessary to assume electron transfer from the outer core band to the valence band, and an increase of valence electron number for calcium from 2 to ∼ 3.5. This assumption is supported by the Fermi sphere-Brillouin zone interaction model that increases under compression. The recently found structure of Ca-VII with a tetragonal cell containing 32 atoms (tI32) is similar to that in the intermetallic compound In5Bi3 with 3.75 valence electrons per atom. Structural relations are analyzed in terms of electronic structure resemblance. Correlations of structure and physical properties of Ca are discussed.
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Affiliation(s)
- Valentina F Degtyareva
- Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow Province 142432, Russian Federation
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Holzapfel WB. Structures of the elements - crystallography and art. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2014; 70:429-435. [PMID: 24892589 DOI: 10.1107/s2052520614005277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 03/07/2014] [Indexed: 06/03/2023]
Abstract
Since simple data tables on phase transitions and structural systematics of the elements over a wide range of pressure and temperature are difficult to comprehend, this paper illustrates these systematics with some artwork together with an artist's view of the equations of states for the elements.
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Affiliation(s)
- Wilfried B Holzapfel
- Physics Department, University of Paderborn, Warburger Str. 100, D-33095 Paderborn, Germany
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Dera P. A simple approach to understand the high-pressure calcium conundrum. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2014; 70:401-402. [PMID: 24892585 DOI: 10.1107/s2052520614011640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 05/20/2014] [Indexed: 06/03/2023]
Affiliation(s)
- Przemyslaw Dera
- Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, 680 East-West Road, Manoa, HI 96822, USA
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Cheng XY, Chen XQ, Li DZ, Li YY. Computational materials discovery: the case of the W–B system. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2014; 70:85-103. [DOI: 10.1107/s2053229613027551] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 10/01/2013] [Indexed: 11/11/2022]
Abstract
By means of variable-compositional evolutionary algorithms, in combination with first-principles calculations, the compositions, structures and mechanical properties of the W–B system have been theoretically investigated. As well as confirming the experimental observations (including their crystal structures) for the four known compounds W2B, WB, WB2and WB3, the new stable compound W8B7and two nearly stable compounds, W2B3and WB4, have also been predicted in the ground state. The elastic properties and estimated Vickers hardnesses of all these borides have been systematically derived. The results show that, among these borides,hP6-WB2exhibits the largest ultra-incompressibility along thecaxis, with the highestC33value (953 GPa, comparable with that of the most incompressible diamond).hP16-WB3exhibits the highest hardness of 36.9 GPa, in good agreement with the experimentally measured data from 28.1 to 43.3 GPa, close to the superhard threshold, andoC8-WB shows the highest bulk modulus of about 350 GPa. The new stable compound W8B7crystallizes in the monoclinicmP15 phase, with infinite zigzag B chains running parallel to the W-atom layers, resulting in a relatively high estimated hardness of 19.6 GPa. The anisotropic Young's modulusEand torsion shear modulusGthave been derived for bothoC8-WB andhP16-WB3. The current state of research and the historic inconsistency of the W–B system are briefly summarized, in particular clarifying the fact that the previous experimentally attributedhP20-WB4is in fact the defect-containinghP16-WB3.
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