On the Heat Capacity, Entropy, and “Glass Transition” of Vitreous Ice

Abstract

AbstractAn analysis of the thermal properties of vitreous ice shows that both its heat capacity Cp and its entropy above 100 K are partly configurational in origin. The configurational contribution increases with temperature, and the excess Cp and entropy near the solid-liquid transformation temperature are 36.7 and 2.1 J K-1 mo1-1, respectively. The increase is interpreted as indicating the onset of molecular mobility in vitreous ice. The configurational Cp, of the melt of vitreous ice at 133.6 K, of ≈ 36.7 J K-1 mo1-1, is the same as the configurational Cp, of water at 273 K. Thus, the short-range order in the melt differs little from that in water at 273 K. The maximum calorimetric residual entropy of vitreous ice is 13.4 J K-1 mol-1, which is in fair agreement with the maximum value of 9.2 J K-1 mol-1 anticipated for a tetrahedral random-network model with fully disordered positions of H atoms. Thermodynamic consideration of a glass transition in supercooled liquid water indicates that there is no continuity of state between supercooled water and vitreous ice and, therefore, the structure and thermodynamic properties of a possible glassy state of water should be different from that of vapour-deposited vitreous ice. This paper is published in full in Philosophical Magazine, Eighth Ser., Vol. 35, No. 4, 1977, p. 1077-90.