Low-Pressure Electrochemical Synthesis of Complex High-Pressure Superconducting Superhydrides

Pin-Wen Guan, Ying Sun, Russell J. Hemley, Hanyu Liu, Yanming Ma, and Venkatasubramanian Viswanathan
Phys. Rev. Lett. 128, 186001 – Published 6 May 2022
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Abstract

There is great current interest in multicomponent superhydrides due to their unique quantum properties under pressure. A remarkable example is the ternary superhydride Li2MgH16 computationally identified to have an unprecedented high superconducting critical temperature Tc of 470K at 250 GPa. However, the very high synthesis pressures required remains a significant hurdle for detailed study and potential applications. In this Letter, we evaluate the feasibility of synthesizing ternary Li-Mg superhydrides by the recently proposed pressure-potential (P2) method that uniquely combines electrochemistry and applied pressure to control synthesis and stability. The results indicate that it is possible to synthesize Li-Mg superhydrides at modest pressures by applying suitable electrode potentials. Using pressure alone, no Li-Mg ternary hydrides are predicted to be thermodynamically stable, but in the presence of electrode potentials, both Li2MgH16 and Li4MgH24 can be stabilized at modest pressures. Three polymorphs are predicted as ground states of Li2MgH16 below 300 GPa, with transitions at 33 and 160 GPa. The highest pressure phase is superconducting, while the two at lower pressures are not. Our findings point out the potentially important role of the P2 method in controlling phase stability of complex multicomponent superhydrides.

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  • Received 7 October 2021
  • Accepted 15 March 2022

DOI:https://doi.org/10.1103/PhysRevLett.128.186001

© 2022 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Pin-Wen Guan1, Ying Sun2, Russell J. Hemley3, Hanyu Liu2, Yanming Ma2,4, and Venkatasubramanian Viswanathan1,5,*

  • 1Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
  • 2International Center of Computational Method and Software and State Key Laboratory for Superhard Materials, College of Physics, Jilin University, Changchun 130012, China
  • 3Departments of Physics, Chemistry, and Earth and Environmental Sciences, University of Illinois Chicago, Chicago, Illinois 60607, USA
  • 4International Center of Future Science, Jilin University, Changchun 130012, China
  • 5Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA

  • *venkvis@cmu.edu

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Vol. 128, Iss. 18 — 6 May 2022

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