A new structural relaxation pathway of low-density amorphous ice

Area of Science:

• Materials Science
• Cosmology
• Physical Chemistry

Background:

• Low-density amorphous (LDA) ice is crucial for cosmological processes.
• Understanding LDA ice's structural diversity and heating dynamics is incomplete.
• LDA ice is one of at least two distinct amorphous ice forms.

Purpose of the Study:

• Investigate the structural diversity of LDA ice formed from heating ice VIII.
• Characterize the dynamic processes and phase transitions during LDA formation from ice VIII.
• Compare LDA ice derived from ice VIII with traditionally annealed LDA states.

Main Methods:

• X-ray diffraction
• Raman spectroscopy
• Temperature-induced amorphisation of ice VIII at ambient pressure

Main Results:

• LDA ice from ice VIII shows unique structural differences from annealed LDA.
• A novel relaxation pathway increases intermediate-range order in this LDA.
• Local structure is initially more ordered and becomes disordered upon annealing.
• Phase transitions include ice IX formation, potentially linked to LDA peculiarities.

Conclusions:

• LDA ice is more structurally diverse than previously understood.
• Heating ice VIII offers a new route to LDA ice with distinct properties.
• The findings challenge existing models of amorphous ice structures and relaxation pathways.