Effects of stacking disorder on thermal conductivity of cubic ice
2015 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, no 5, 054505Article in journal (Refereed) Published
Cubic ice is said to have stacking disorder when the H2O sequences in its structure (space group Fd (3) over barm) are interlaced with hexagonal ice (space group P6(3)/mmc) sequences, known as stacking faults. Diffraction methods have shown that the extent of this disorder varies in samples made by different methods, thermal history, and the temperature T, but other physical properties of cubic and hexagonal ices barely differ. We had found that at 160 K, the thermal conductivity, kappa, of cubic ice is similar to 20% less than that of hexagonal ice, and this difference varies for cubic ice samples prepared by different methods and/or subjected to different thermal history. After reviewing the methods of forming cubic ice, we report an investigation of the effects of stacking disorder and other features by using new data, and by analyzing our previous data on the dependence of kappa on T and on the pressure. We conclude that the lower kappa of cubic ice and its weaker T-dependence is due mainly to stacking disorder and small crystal sizes. On in situ heating at 20-50 MPa pressure, kappa increases and cubic ice irreversibly transforms more sharply to ice Ih, and at a higher T of similar to 220 K, than it does in ex situ studies. Cooling and heating between 115 and 130 K at 0.1 K min(-1) rate yield the same kappa value, indicating that the state of cubic ice in these conditions does not change with time and T. The increase in kappa of cubic ice observed on heat-annealing before its conversion to hexagonal ice is attributed to the loss of stacking faults and other types of disorders, and to grain growth. After discussing the consequences of our findings on other properties, we suggest that detailed studies of variation of a given property of cubic ice with the fraction of stacking faults in its structure may reveal more about the effect of this disorder. A similar disorder may occur in the mono-layers of H2O adsorbed on a substrate, in bulk materials comprised of two dimensional layers, in diamond and in Zirconium and in numerous other crystals.
Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015. Vol. 143, no 5, 054505
Atom and Molecular Physics and Optics
IdentifiersURN: urn:nbn:se:umu:diva-108140DOI: 10.1063/1.4927566ISI: 000359377200028PubMedID: 26254659OAI: oai:DiVA.org:umu-108140DiVA: diva2:855105