Infrared Absorption Study of High-Pressure Ice-VII Phase.

Elastic Properties in High Pressure ICe•VII Phase

The pressure dependences of sound velocities, refractive index and elastic constants in ice-VII phase have been determined up to 8 GPa at 300 K by high-pressure Brillouin spectroscopy developed for a single molecular crystal grown in a diamond anvil cell. The Cauchy relation of C12=C44 was found at each pressure. This result suggests that the interactions between the oxygen atoms can be describ...

Protonic diffusion in high-pressure ice VII.

Near ambient pressures, molecular diffusion dominates protonic diffusion in ice. Theoretical studies have predicted that protonic diffusion will dominate at high pressures in ice. We measured the protonic diffusion coefficient for the highest temperature molecular phase of ice VII at 400 kelvin over its entire stable pressure region. The values ranged from 10(-17) to 10(-15) square meters per s...

New high-pressure phase of ice.

Convergent Raman features in high density amorphous ice, ice VII, and ice VIII under pressure.

The high-pressure behavior of H(2)O ice at temperatures below 100 K has been investigated to 20 GPa by Raman spectroscopy. Between 10 and 80 K, high density amorphous (hda) ice formed from ice I(h) undergoes a phase transition near 5 GPa to ice VII' and a transition at 14 GPa to a different phase. At 14 GPa, a new low-frequency band appears at ~150 cm(-1) that steeply increases in frequency wit...

The phase diagram of high-pressure superionic ice

Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets. In superionic ice liquid hydrogen coexists with a crystalline oxygen sublattice. At high pressures, the properties of superionic ice are largely unknown. Here we report evidence that from 280 GPa to 1.3 TPa, there are several competing phases within the close-pac...