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 I_h to occur at T_Ih–XI = 58.9 K and T_XI–Ih = 73.4 K. For D₂O, T_Ih–XI = 63.7 K and T_XI–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 I_h, II and XI coexist. A first order phase transition with kinetic broadening associated with proton ordering dynamics is identified at 100 K.