Thermal conductivity of allotropic modifications of ice

Abstract

THE pressure–temperature phase diagram of H₂O comprises several solid phases, differing in their crystal structure (Fig. I)¹. Ice offers an unusual opportunity for investigating how the different modes of stacking and the slight distortions of otherwise identical molecules influence the conduction of heat. There are no previous studies of the thermal conductivity of ice, except for the phase Ih at atmospheric pressure. We report here the first measurements of the thermal conductivity of the high pressure forms II, III, V and VI. Each of these modifications has a higher density, and a lower thermal conductivity, than ordinary ice, Ih. Ice Ih seems to be the first example of an insulator which has a decreasing thermal conductivity under increasing pressure. Our findings show that all these forms of ice have a positive thermal expansion coefficient.