Amorphous and crystalline ices studied by dielectric spectroscopy

Area of Science:

• Physical Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Amorphous ices exhibit complex dielectric responses.
• Distinguishing between amorphous and crystalline ice forms is crucial for understanding water's phase behavior.
• Previous studies have explored amorphous ices but a comprehensive comparison with crystalline forms using dielectric measurements is needed.

Purpose of the Study:

• To investigate frequency-dependent dielectric properties of various amorphous and crystalline ices.
• To compare the dielectric spectral shapes and dipolar time scales of different ice phases.
• To determine effective methods for differentiating amorphous from crystalline ices using dielectric spectroscopy.

Main Methods:

• Ambient-pressure dielectric measurements across a range of frequencies.
• Analysis of loss spectra to determine dipolar time scales and spectral shapes.
• Comparison of experimental data with literature values for amorphous ices and amorphous solid water.

Main Results:

• Hyperquenched glassy water, ice IV, ice VI, and a CO2-filled clathrate hydrate were measured.
• Amorphous ices showed a trend of increasing dynamic heterogeneity with increasing density.
• Amorphous ices exhibited a curved high-frequency wing in their loss spectra, while crystalline ices showed power-law behavior.
• Relaxation times of crystalline ices fell between those of low-density and high-density amorphous ice.

Conclusions:

• Spectral shape analysis provides insights into the amorphicity or crystallinity of ice samples.
• Doping amorphous ices appears to be the most effective dielectric spectroscopy method for distinguishing them from crystalline ices.
• Further research into the dynamic heterogeneity of various ice phases is warranted.