Growth of Ice IV and Equilibrium Curves between Liquid Water, Ice IV, Ice V and Ice VI

The phase diagram of water at moderate pressures is studied by a dielectric measurement for solid-solid transitions and further by a volume change method for liquid-ice VI transition. The metastable phase ice IV can be made from ice VI on decreasing the pressure at temperatures from -13.6 to -14.6°C. The growth and the metastability region of ice IV are described. The liquid-ice IV-ice VI and liquid-ice V-ice VI triple points are located at 5567 bar, -6.62°C and at 6343 bar, +0.22°C, respectively. Among the phase boundaries investigated only the liquid-ice VI transition is useful as a fixed point for pressure calibration.