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

Shuyin Yu (1) , Qingfeng Zeng (1) , Artem R. Oganov (2, 3) , Chaohao Hu , Gilles Frapper (4) , Litong Zhang (1)

1 TSCM - National Key State Laboratory for ThermoStructural Composites
2 MIPT - Moscow Institute of Physics and Technology [Moscow]
3 SBU - Stony Brook University [SUNY]
4 IC2MP [Poitiers] - Institut de chimie des milieux et matériaux de Poitiers [UMR 7285]

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 -> P (3) over bar m1 -> R (3) over barm -> Cmcm -> P4/nmm, which occur at 24, 139, 204 and 349 GPa, respectively. P (3) over bar m1 and R (3) over barm 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. P (3) over bar m1 and R (3) over barm 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 lambda=0.63 for Cmcm with a T-c of 32.1-44.1 K at 250 GPa and lambda=0.65 for P4/nmm with a T-c of 46.1-62.4 K at 400 GPa. The dependence of T-c on pressure indicates that T-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. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

Domaines: Sciences de la Terre

Shuyin Yu, Qingfeng Zeng, Artem R. Oganov, Chaohao Hu, Gilles Frapper, et al.. Exploration of stable compounds, crystal structures, and superconductivity in the Be-H system. AIP Advances, 2014, 4 (10), ⟨10.1063/1.4898145⟩. ⟨hal-01324799⟩