Title

Exotic Hydrogen Bonding in Compressed Ammonia Hydrides

Document Type

Article

Publication Date

5-8-2019

Publication Title

Journal of Physical Chemistry Letters

Volume

10

Issue

11

First page number:

2761

Last page number:

2766

Abstract

Hydrogen-rich compounds attract significant fundamental and practical interest for their ability to accommodate diverse hydrogen bonding patterns and their promise as superior energy storage materials. Here, we report on an intriguing discovery of exotic hydrogen bonding in compressed ammonia hydrides and identify two novel ionic phases in an unusual stoichiometry NH7. The first is a hexagonal R3̅m phase containing NH3–H+–NH3, H–, and H2 structural units stabilized above 25 GPa. The exotic NH3–H+–NH3 unit comprises two NH3 molecules bound to a proton donated from a H2 molecule. Above 60 GPa, the structure transforms to a tetragonal P41212 phase comprising NH4+, H–, and H2 units. At elevated temperatures, fascinating superionic phases of NH7 with part-solid and part-liquid structural forms are identified. The present findings advance fundamental knowledge about ammonia hydrides at high pressure with broad implications for studying planetary interiors and superior hydrogen storage materials.

Disciplines

Physical Chemistry

Language

English

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