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Morgan HWT, Alexandrova AN. Structures of LaH 10, EuH 9, and UH 8 superhydrides rationalized by electron counting and Jahn-Teller distortions in a covalent cluster model. Chem Sci 2023; 14:6679-6687. [PMID: 37350837 PMCID: PMC10283509 DOI: 10.1039/d3sc00900a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 05/30/2023] [Indexed: 06/24/2023] Open
Abstract
The superconducting hydrides LaH10, EuH9 and UH8 are studied using chemically intuitive bonding analysis of periodic and molecular models. We find trends in the crystallographic and electronic structures of the materials by focusing on chemically meaningful building blocks in the predicted H sublattices. Atomic charge calculations, using two complementary techniques, allow us to assign oxidation states to the metals and divide the H sublattice into neutral and anionic components. Cubic [H8]q- clusters are an important structural motif, and molecular orbital analysis of this cluster in isolation shows the crystal structures to be consistent with our oxidation state assignments. Crystal orbital Hamilton population analysis confirms the applicability of the cluster model to the periodic electronic structure. A Jahn-Teller distortion predicted by MO analysis rationalises the distortion observed in a prior study of EuH9. The impact of this distortion on superconductivity is determined, and implications for crystal structure prediction in other metal-hydrogen systems are discussed. Additionally, the performance of electronic structure analysis methods at high pressures are tested and recommendations for future studies are given. These results demonstrate the value of simple bonding models in rationalizing chemical structures under extreme conditions.
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Affiliation(s)
- Harry W T Morgan
- Department of Chemistry and Biochemistry, University of California Los Angeles California 90095-1569 USA
| | - Anastassia N Alexandrova
- Department of Chemistry and Biochemistry, University of California Los Angeles California 90095-1569 USA
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Hilleke KP, Zurek E. Rational Design of Superconducting Metal Hydrides via Chemical Pressure Tuning**. Angew Chem Int Ed Engl 2022; 61:e202207589. [DOI: 10.1002/anie.202207589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Indexed: 11/11/2022]
Affiliation(s)
- Katerina P. Hilleke
- Department of Chemistry State University of New York at Buffalo Buffalo NY 14260-3000 USA
| | - Eva Zurek
- Department of Chemistry State University of New York at Buffalo Buffalo NY 14260-3000 USA
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Hilleke K, Zurek E. Rational Design of Superconducting Metal Hydrides via Chemical Pressure Tuning. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202207589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Katerina Hilleke
- State University of New York at Buffalo: University at Buffalo Department of Chemistry 359 Natural Sciences ComplexUniversity at Buffalo, North Campus 14260-3000 Buffalo UNITED STATES
| | - Eva Zurek
- University at Buffalo, State University of New York Department of Chemistry 331 Natural Sciences Complex 14260 Buffalo UNITED STATES
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Zarif M, Spiteri RJ, Bowles RK. Inherent structure landscape of hard spheres confined to narrow cylindrical channels. Phys Rev E 2021; 104:064602. [PMID: 35030837 DOI: 10.1103/physreve.104.064602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 11/10/2021] [Indexed: 06/14/2023]
Abstract
The inherent structure landscape for a system of hard spheres confined to a hard cylindrical channel, such that spheres can only contact their first and second neighbors, is studied using an analytical model that extends previous results [Phys. Rev. Lett. 115, 025702 (2015)PRLTAO0031-900710.1103/PhysRevLett.115.025702] to provide a comprehensive picture of jammed packings over a range of packing densities. In the model, a packing is described as an arrangement of k helical sections, separated by defects, that have alternating helical twist directions and where all spheres satisfy local jamming constraints. The structure of each helical section is determined by a single helical twist angle, and a jammed packing is obtained by minimizing the length of the channel per particle with respect to the k helical section angles. An analysis of a small system of N=20 spheres shows that the basins on the inherent structure landscape associated with these helical arrangements split into a number of distinct jammed states separated by low barriers giving rise to a degree of hierarchical organization. The model accurately predicts the geometric properties of packings generated using the Lubachevsky and Stillinger compression scheme (N=10^{4}) and provides insight into the nature of the probability distribution of helical section lengths.
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Affiliation(s)
- Mahdi Zarif
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Tehran 19839-9411, Iran
| | - Raymond J Spiteri
- Department of Computer Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9, Canada
| | - Richard K Bowles
- Department of Chemistry, University of Saskatchewan, SK, S7N 5C9, Canada
- Centre for Quantum Topology and its Applications (quanTA), University of Saskatchewan, SK S7N 5E6, Canada
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Koshoji R, Ozaki T. Densest ternary sphere packings. Phys Rev E 2021; 104:024101. [PMID: 34525636 DOI: 10.1103/physreve.104.024101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 07/08/2021] [Indexed: 11/07/2022]
Abstract
We present our exhaustive exploration of the densest ternary sphere packings (DTSPs) for 45 radius ratios and 237 kinds of compositions, which is a packing problem of three kinds of hard spheres with different radii, under periodic boundary conditions by a random structure searching method. To efficiently explore DTSPs we further develop the searching method based on the piling-up and iterative balance methods [Koshoji et al., Phys. Rev. E 103, 023307 (2021)2470-004510.1103/PhysRevE.103.023307]. The unbiased exploration identifies diverse 38 putative DTSPs appearing on phase diagrams in which 37 DTSPs of them are discovered in the study. The structural trend of DTSPs changes depending especially on the radius of small spheres. In case that the radius of small spheres is relatively small, structures of many DTSPs can be understood as derivatives of densest binary sphere packings (DBSPs), while characteristic structures specific to the ternary system emerge as the radius of small spheres becomes larger. In addition to DTSPs, we reveal a lot of semi-DTSPs (SDTSPs) which are obtained by excluding DBSPs in the calculation of phase diagram, and investigate the correspondence of DTSPs and SDTSPs with real crystals based on the space group, showing a considerable correspondence of SDTSPs having high symmetries with real crystals including Cu_{2}GaSr and ThCr_{2}Si_{2} structures. Our study suggests that the diverse structures of DBSPs, DTSPs, and SDTSPs can be effectively used as structural prototypes for searching complex crystal structures.
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Affiliation(s)
- Ryotaro Koshoji
- Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
| | - Taisuke Ozaki
- Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan
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Peña-Alvarez M, Binns J, Martinez-Canales M, Monserrat B, Ackland GJ, Dalladay-Simpson P, Howie RT, Pickard CJ, Gregoryanz E. Synthesis of Weaire-Phelan Barium Polyhydride. J Phys Chem Lett 2021; 12:4910-4916. [PMID: 34008402 DOI: 10.1021/acs.jpclett.1c00826] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
By combining pressures up to 50 GPa and temperatures of 1200 K, we synthesize the novel barium hydride, Ba8H46, stable down to 27 GPa. We use Raman spectroscopy, X-ray diffraction, and first-principles calculations to determine that this compound adopts a highly symmetric Pm3¯n structure with an unusual 534:1 hydrogen-to-barium ratio. This singular stoichiometry corresponds to the well-defined type-I clathrate geometry. This clathrate consists of a Weaire-Phelan hydrogen structure with the barium atoms forming a topologically close-packed phase. In particular, the structure is formed by H20 and H24 clathrate cages showing substantially weakened H-H interactions. Density functional theory (DFT) demonstrates that cubic Pm3¯n Ba8H46 requires dynamical effects to stabilize the H20 and H24 clathrate cages.
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Affiliation(s)
- Miriam Peña-Alvarez
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh EH8 8AQ, U.K
| | - Jack Binns
- Center for High Pressure Science and Technology Advanced Research, Shanghai 100094, P.R. China
| | - Miguel Martinez-Canales
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh EH8 8AQ, U.K
| | - Bartomeu Monserrat
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Graeme J Ackland
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh EH8 8AQ, U.K
| | - Philip Dalladay-Simpson
- Center for High Pressure Science and Technology Advanced Research, Shanghai 100094, P.R. China
| | - Ross T Howie
- Center for High Pressure Science and Technology Advanced Research, Shanghai 100094, P.R. China
| | - Chris J Pickard
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, U.K
- Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
| | - Eugene Gregoryanz
- Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh EH8 8AQ, U.K
- Center for High Pressure Science and Technology Advanced Research, Shanghai 100094, P.R. China
- Key Laboratory of Materials Physics, Institute of Solid State Physics, CAS, Hefei 230031, P.R. China
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