PHASE-TRANSITION AND ENTROPY OF AMORPHOUS ICES

Mishima's recent data [J. Chem. Phys. 100, 5910 (1994)], showing that the isothermal interconversion of low- and high-density forms of pressure amorphized ice is of first order thermodynamically, have been analyzed in terms of the configurational entropy. At the equilibrium pressure of 2 kbar and 135 K, the entropy of transformation is zero or negligible so that the configurational entropy of the two forms is about the same. This distinguishes the low-density form (whose entropy is about 3J/mol/K higher than that of hexagonal ice) from the hyperquenched glassy water. Comparison of calorimetric and relaxation behaviors of the pressure-amorphized low density and hyperquenched glassy water also indicates that their structures differ. Reasons for this difference are given and the low magnitude of the residual entropy of glassy water is discussed. It is argued that model-based calculations of residual entropy do not yield a plausible value for liquids. © 1995 American Institute of Physics.