NEUTRON-SCATTERING STUDIES OF ICE PREPARED BY DIFFERENT THERMOBARIC TREATMENTS

On heating the recovered high-pressure phase ice VIII at ambient press ure, the transitions to high-density amorphous (hda) and low-density a morphous ices, to cubic ice Ic, and finally to hexagonal ice Ih were o bserved using real-time neutron diffraction. A new form of ice, ''defe ctive ice VI'', was prepared for the fist time by pressurizing ice Ih to 30 kbar at liquid nitrogen temperature. Vibrational spectra of ices Ih, hda, VI, VI', and VIII prepared by different thermobaric treatmen ts were studied by inelastic neutron scattering. The translational ban d of the intermolecular part of ice VI' vibrational spectrum was shown to be similar to that of hda ice, whereas its Librational band was si milar to that of ice VI. We conclude that ices VI, VI', and hda have e ssentially the same atomic correlations and force constants, though wi th the different degree of disorder in the case of ices VI' and hda.