文摘
The high-pressure behavior of H2O 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 Ih undergoes a phase transition near 5 GPa to ice VII鈥?and a transition at 14 GPa to a different phase. At 14 GPa, a new low-frequency band appears at 150 cm鈭? that steeply increases in frequency with pressure. The phase can be recovered to 0.1 MPa at temperatures below 80 K, and it transforms to low density amorphous ice (lda) upon heating. The phase is only present below 140 K and has spectral features that are identical to the phase formed from ice VIII at these pressures and temperatures. Similar changes have been observed in ice VII at these pressures but at room temperature. The results suggest structural changes having a common origin.