Proton ordering dynamics of H2O ice.

From high precision measurements of the complex dielectric constant of especially prepared samples of H2O, we identify the onset temperatures of the phase transition into and out of ice XI from ice Ih to occur at TIh-XI = 58.9 K and TXI-Ih = 73.4 K. For D2O, TIh-XI = 63.7 K and TXI-Ih = 78.2 K. A triple point is identified to exist at 0.07 GPa and 73.4 K for H2O and 0.08 GPa and 78.2 K for D2O where ices Ih, II and XI coexist. A first order phase transition with kinetic broadening associated with proton ordering dynamics is identified at 100 K.