Pressure-Induced Superionicity of H- in Hypervalent Sodium Silicon Hydrides.


Type
Article
Change log
Authors
Liang, Tianxiao 
Zhang, Zihan 
Yu, Hongyu 
Cui, Tian 
Feng, Xiaolei 
Abstract

Superionic states simultaneously exhibit properties of a fluid and a solid. Proton (H+) superionicity in ice, H3O, He-H2O, and He-NH3 compounds is well-studied. However, hydride (H-) superionicity in H-rich compounds is rare, being associated with instability and strongly reducing conditions. Silicon, sodium, and hydrogen are abundant elements in many astrophysical bodies. Here, we use first-principles calculations to show that, at high pressure, Na, Si, and H can form several hypervalent compounds. A previously unreported superionic state of Na2SiH6 results from unconstrained H- in the hypervalent [SiH6]2- unit. Na2SiH6 is dynamically stable at low pressure (3 GPa), becoming superionic at 5 GPa, and re-entering solid/fluid states at about 25 GPa. Our observation of H- transport opens up a new field of H- conductors. It also has implications for the formation of conducting layers at depth in exotic carbon exoplanets, potentially enhancing the habitability of such planets.

Description
Keywords
51 Physical Sciences, 5104 Condensed Matter Physics
Journal Title
J Phys Chem Lett
Conference Name
Journal ISSN
1948-7185
1948-7185
Volume Title
12
Publisher
American Chemical Society (ACS)
Rights
All rights reserved
Sponsorship
Engineering and Physical Sciences Research Council (EP/P022596/1)