Measurement of the heat capacities of the liquid, glass, and crystal (α-polymorph) forms of ZnCl2, and of the pressure dependence of the glass transition temperature, are reported. The excess heat capacity, and the temperature dependence of the viscosity as well, may be described using two-parameter equations from the bond-lattice model. The glass transition temperature at a given pressure is independent, within experimental error, of the pressure-temperature history of the sample. The observed pressure dependence, however, is only half the value predicted from the changes in heat capacity and expansion coefficient at Tg by the Davies-Jones equation. This uncommon failure of the equation is attributed to a small ΔCp associated with the network structure of zinc chloride.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry