Exploration of stable compounds, crystal structures, and superconductivity in the Be-H system
Abstract
Using first-principles variable-composition evolutionary methodology, we explored the high-pressure structures of beryllium hydrides between 0 and 400 GPa. We found that BeH2 remains the only stable compound in this pressure range. The pressure-induced transformations are predicted as Ibam→P3̄m1→R3̄m→Cmcm→P4/nmm, which occur at 24, 139, 204 and 349 GPa, respectively. P3̄m1 and R3̄m 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. P3̄m1 and R3̄m 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 Tc of 32.1-44.1 K at 250 GPa and λ = 0.65 for P4/nmm with a Tc of 46.1-62.4 K at 400 GPa. The dependence of Tc on pressure indicates that Tc 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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 01, 2014
- Source ID
- 10.1063/1.4898145
Entities
People
- Artem Oganov
- Chaohao Hu
- Gilles Frapper
- Litong Zhang
- Qingfeng Zeng
- Shuyin Yu
Organizations
- Guilin University of Electronic Technology
- Moscow Institute of Physics and Technology
- National Science Foundation
- Northwestern Polytechnical University
- State University of New York
- University of Poitiers