In-situ Raman study of the pressure-induced bulk melting of hexagonal ice

We have investigated a series of changes in in-situ Raman spectra as a function of pressure at 264 K to study the process of bulk melting in I-h (hexagonal ice) to the liquid water. We succeeded in measuring spectra where ice I-h coexists with liquid water at an equilibrium pressure of 0.1 GPa. The lowest frequency peak which is derived from the strong hydrogen-bonds of ice I-h lattice remains until the transition and the fraction of liquid water at this equilibrium increases upon compression. The results are interpreted in the context of pre-melting effects in the ice particles.