Structure of crystalline water ice formed through neon matrix sublimation under cryogenic and vacuum conditions

TL;DR

This study demonstrates that cubic ice Ic can be formed at 13 K through neon matrix sublimation, revealing a new low-temperature pathway for crystalline ice formation with less stacking disorder than vapor-deposited ice.

Contribution

The paper introduces a novel low-temperature sublimation method using neon matrices to produce crystalline ice Ic with minimal stacking disorder at 13 K.

Findings

Crystalline ice Ic formed at 13 K via neon sublimation.

Less stacking disorder in neon sublimation ice compared to vapor-deposited ice.

Amorphous water initially forms, then transitions to cubic ice during sublimation.

Abstract

Ice I has three forms depending on the stacking arrangements of its layers: hexagonal ice Ih, cubic ice Ic, and stacking disordered ice Isd. Below ~60 K, amorphous water becomes metastable, and the formation of any form of ice I is often implicitly precluded. Using a newly developed low-temperature reflection high-energy electron diffraction (RHEED) technique, we show that crystalline ice with cubic stacking sequences (i.e., ice Ic) formed through Ne sublimation from a solid H2O/Ne (1:1000 ratio) matrix at 13 K. The extent of staking disorder (disordered cubic and hexagonal stacking sequences) in the ice formed by Ne matrix sublimation is smaller than that in vapor-deposited ice Isd prepared at 143 K and below the limit of detection of low-temperature RHEED. Dependence of the resulting ice structures on the thickness of the H2O/Ne matrix shows that amorphous water first forms in the early stages of Ne sublimation and the cubic stacking sequence subsequently takes place. As the cubic ice Ic formed here at a much lower temperature (13 K) than previously observed (typically above 78 K), Ne matrix sublimation represents a novel route to the formation of cubic ice Ic under low-temperature and low-pressure conditions.