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Title: Exploration of stable compounds, crystal structures, and superconductivity in the Be-H system

Using first-principles variable-composition evolutionary methodology, we explored the high-pressure structures of beryllium hydrides between 0 and 400 GPa. We found that BeH{sub 2} remains the only stable compound in this pressure range. The pressure-induced transformations are predicted as Ibam→P3{sup -}m1→R3{sup -}m→Cmcm→P4/nmm, which occur at 24, 139, 204 and 349 GPa, respectively. P3{sup -}m1 and R3{sup -}m structures are layered polytypes based on close packings of H atoms with Be atoms filling all octahedral voids in alternating layers. Cmcm and P4/nmm contain two-dimensional triangular networks with each layer forming a kinked slab in the ab-plane. P3{sup -}m1 and R3{sup -}m are semiconductors while Cmcm and P4/nmm are metallic. We have explored superconductivity of both metal phases, and found large electron-phonon coupling parameters of λ = 0.63 for Cmcm with a T{sub c} of 32.1-44.1 K at 250 GPa and λ = 0.65 for P4/nmm with a T{sub c} of 46.1-62.4 K at 400 GPa. The dependence of T{sub c} on pressure indicates that T{sub c} initially increases to a maximum of 45.1 K for Cmcm at 275 GPa and 97.0 K for P4/nmm at 365 GPa, and then decreases with increasing pressure for both phases.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Science and Technology on Thermostructural Composite Materials Laboratory, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China)
  2. Department of Geosciences, Center for Materials by Design, and Institute for Advanced Computational Science, State University of New York, Stony Brook, NY 11794-2100 (United States)
  3. (Russian Federation)
  4. (China)
  5. School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004 (China)
  6. IC2MP UMR 7285, Université de Poitiers - CNRS, Poitiers 86022 (France)
Publication Date:
OSTI Identifier:
22299618
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 4; Journal Issue: 10; Other Information: (c) 2014 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BERYLLIUM HYDRIDES; ELECTRON-PHONON COUPLING; ORTHORHOMBIC LATTICES; PRESSURE RANGE GIGA PA; SUPERCONDUCTIVITY; TETRAGONAL LATTICES