Immiscibility in N₂-H₂O solids up to 140 GPa.

Area of Science:

• Geophysics
• Materials Science
• Chemistry

Background:

• Nitrogen and water are abundant, but their reactions under extreme pressure-temperature conditions are poorly understood.
• Previous studies indicated clathrate formation in the H2O-N2 system below 6 GPa.

Purpose of the Study:

• To investigate the chemical reactions and phase behavior of the H2O-N2 system at high pressures up to 140 GPa.
• To determine if mixed compounds or ice doping occur under these extreme conditions.

Main Methods:

• Raman spectroscopy
• X-ray diffraction
• Diamond anvil cell experiments

Main Results:

• Clathrates formed locally above 0.3 GPa and transformed into a fine-grained state above 6 GPa.
• No evidence of mixed H2O-N2 compounds or nitrogen doping of ice was observed.
• Size effects in fine-grained crystallites influenced Raman spectra, but X-ray diffraction confirmed bulk behavior of known solid phases.

Conclusions:

• The H2O-N2 system does not form mixed compounds at high pressures up to 140 GPa.
• Observed spectral changes are attributed to crystallite size effects, not new phase formation.
• Nitrogen does not dope ice, even in nonmolecular nitrogen stability regimes.