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.