1. Division of Chemistry, National Research Council, Ottawa, Canada K1A 0R9

Abstract

Amorphous solids are made mainly by cooling the liquid below the glass transition without crystallizing it, a method used since before recorded history¹, and by depositing the vapour onto a cold plate², as well as by several other methods^3,4. We report here a new way—by 'melting' a solid by pressure below the glass transition of the liquid—and apply it to making a new kind of amorphous ice. Thus, ice I has been transformed to an amorphous phase, as determined by X-ray diffraction, by pressurizing it at 77 K to its extrapolated melting point of 10 kbar. At the melting point, the fluid is well below its glass transition. On heating at a rate of 2.6 K min^-1 at zero pressure it transforms at 117 K to a second amorphous phase with a heat evolution of 428 J g^-1 and at 152 K further transforms to ice I with a heat evolution of 9215 J g^-1. In one sample, ice Ic was formed and in another, existing crystals of ice Ih grew from the amorphous phase. Heating below the 117 K transition causes irreversible changes in the diffraction pattern, and a continuous range of amorphous phases can be made. Similar transformations will probably occur in all solids whose melting point decreases with increasing pressure if they can be cooled sufficiently for a transformation to a crystalline solid to be too slow.