An apparently first-order transition between two amorphous phases of ice induced by pressure

;
• Calvert, L. D.
;
• Whalley, E.

Abstract

We recently reported¹ a transition from ice Ih to a high-density amorphous phase at 10 kbar, 77 K. Here we report that low-density amorphous ice (density 0.94 g cm^-3) compressed at 77 K transforms to high-density amorphous ice (1.19 g cm^-3 at zero pressure) at a sharp transition at 6+/-0.5 kbar. The transition is at least as sharp as the previously reported¹ transition and strongly resembles a first-order transition in its sharpness and large volume change. It appears to be the first example of an apparently first-order transition between amorphous solids and has implications not only for our understanding of the behaviour of condensed matter, but also for theories of planetary interiors.