Isotope effect on the glass transition and crystallization of hyperquenched glassy water Available to Purchase

The thermal behavior of hyperquenched glassy D₂O was investigated by differential scanning calorimetry from 103 to 250 K, in order to investigate the isotope effect on the glass→liquid transition and on the liquid to cubic, and cubic to hexagonal ice. For a heating rate of 30 K min⁻¹ the temperatures of the thermal effects are: 137 K for the onset of the reversible glass→liquid transition (T_g), 154 and 173 K for the beginning and the peak minimum of the crystallization exotherm, and ≊229 K for the peak minimum of the transformation cubic→hexagonal ice. Increase in heat capacity at T_g and the width of the glass transition are similar to those reported for glassy H₂O. T_g of D₂O is higher than that of H₂O by an amount that is expected for isorelaxational and/or isoviscous states assuming that the functional form of the molecular reorientation rates with temperature is unaffected by the isotopic substitution. The increase in the temperature of crystallization of ‘‘fluid’’ D₂O is ≊three times greater than the increase in the glass→liquid transition which causes T_g and devitrification to become more separated in D₂O than in H₂O. Implications of these results for both the inferred λ‐type anomally at ≊228 K in H₂O and at ≊233 K in D₂O, and the presumed formation of a gel‐like structure at these temperatures are discussed.