Ne- and O₂-filled ice XVII: a neutron diffraction study

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Deuterated ice XVII is a metastable solid water polymorph with hexagonal channels.
• Understanding guest molecule incorporation in ice structures is crucial for materials science.
• Previous studies on ice II showed different guest molecule interactions.

Purpose of the Study:

• To investigate the structural behavior of deuterated ice XVII when filled with Ne and O2.
• To determine the location and arrangement of guest molecules within the ice XVII channels.
• To analyze the impact of guest molecules on the host ice's symmetry and stability.

Main Methods:

• In situ neutron diffraction at the ILL (France) was employed.
• Powder patterns were collected for Ne-filled ice XVII (20-50 K) and O2-filled ice XVII (4.6-90 K).
• Rietveld refinement and difference Fourier techniques were used for structural analysis.

Main Results:

• Ne atoms and O2 molecules were located within the hexagonal channels of deuterated ice XVII.
• Guest molecules adopted spiral configurations, preserving P6122 symmetry for Ne and reducing it to P61 for O2.
• Enhanced Ne absorption was observed compared to ice II, attributed to favorable host-guest contacts.
• Attractive O-D interactions in O2-filled ice XVII contributed to structural stabilization.

Conclusions:

• Deuterated ice XVII can incorporate Ne and O2 molecules within its channels.
• The arrangement of guest molecules influences the symmetry of the ice structure.
• Host-guest interactions play a significant role in the stability of filled ice structures.