Thermal conductivity and heat capacity of solid phases of benzene under pressure

Abstract

Using the transient hot-wire method, simultaneous measurements of the thermal conductivity, λ, and the heat capacity per unit volume, ρc _p, were made for solid phases I and II of benzene (C₆H₆). Data were obtained over the temperature range 105 K to 375 K, and at pressures up to 2·4 GPa. At 300 K, the I → II transition was sluggish, so phase I could be retained over a pressure range where it was metastable with respect to phase II. At about 1·2 GPa and 375 K, λ for phase II is detectably greater than for phase I, but at 300 K the two values are almost equal. The value of c _p for phase I was found to decrease by about 10 per cent over the range 0–1 GPa and to remain essentially constant at higher pressures. Values of c _p in phases I and II were found to be equal at all temperatures. The temperature and volume dependences of λ are discussed in relation to current theoretical ideas.