High-density amorphous ice. III. Thermal properties

Abstract

The thermal properties of high-density amorphous ice, which is made by ‘‘melting’’ ice I at 77 K by applying a pressure of ∼10 kbar, have been measured in an automated Tian–Calvet calorimeter. The samples were heated from 78 to 270 K at a rate of 10 K h−1 and heat amounting to 544, 1425, and 35.5 J mol−1 was evolved in one run at the sharp transitions from high-density to low-density amorphous ice, from the low-density amorph to ice Ic, and from ice Ic to Ih, respectively. In addition, heat was spontaneously evolved by the high-density amorph before the transition, and by the sample over a range of ∼50 K around the temperature of the transition from ice Ic to Ih.