Hexagonal and Cubic Ice at Low Temperatures

Abstract

AbstractThe formation of hexagonal and cubic forms of ice was studied by the use of a cold stage in an electron microscope within the temperature range −90° to −180° C. Ice crystal specimens were made on cold substrates, i.e. a collodion film, gold foil, or copper grid on the specimen holder of the cold stage. The hexagonal form of ice formed on the cold substrates at temperatures from−90° to−100° C. At −100° to −130° C, both hexagonal and cubic forms of ice were detected. From −130° to −160° C only cubic ice was found. At temperatures below −160° C, minute crystals of cubic ice were detected. No transformation of the structural form of ice from hexagonal to cubic or from cubic to hexagonal occurred when the temperature of the specimens was varied in the range −90° to −160° C. The lattice constants of hexagonal and cubic ice, and the coefficient of thermal expansion of ice were calculated from the experimental results.