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Is high-density amorphous ice simply a “derailed” state along the ice I to ice IV pathway?

Shephard, Jacob J.; Ling, Sanliang; Sosso, Gabriele C.; Michaelides, Angelos; Slater, Ben; Salzmann, Christoph G.


Jacob J. Shephard

Gabriele C. Sosso

Angelos Michaelides

Ben Slater

Christoph G. Salzmann


The structural nature of high-density amorphous ice (HDA), which forms through low-temperature pressure-induced amorphization of the “ordinary” ice I, is heavily debated. Clarifying this question is important for understanding not only the complex condensed states of H2O but also in the wider context of pressure-induced amorphization processes, which are encountered across the entire materials spectrum. We first show that ammonium fluoride (NH4F), which has a similar hydrogen-bonded network to ice I, also undergoes a pressure collapse upon compression at 77 K. However, the product material is not amorphous but NH4F II, a high-pressure phase isostructural with ice IV. This collapse can be rationalized in terms of a highly effective mechanism. In the case of ice I, the orientational disorder of the water molecules leads to a deviation from this mechanism, and we therefore classify HDA as a “derailed” state along the ice I to ice IV pathway.


Shephard, J. J., Ling, S., Sosso, G. C., Michaelides, A., Slater, B., & Salzmann, C. G. (2017). Is high-density amorphous ice simply a “derailed” state along the ice I to ice IV pathway?. Journal of Physical Chemistry Letters, 8(7), 1645-1650.

Journal Article Type Article
Acceptance Date Mar 21, 2017
Online Publication Date Mar 27, 2017
Publication Date Apr 6, 2017
Deposit Date Nov 20, 2018
Publicly Available Date Nov 20, 2018
Journal Journal of Physical Chemistry Letters
Print ISSN 1948-7185
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 8
Issue 7
Pages 1645-1650
Public URL
Publisher URL


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