Nature of amorphous polymorphism of water

• Published in: Physical review letters Vol. 94; no. 12; p. 125506
• Main Authors: Koza, M M, Geil, B, Winkel, K, Köhler, C, Czeschka, F, Scheuermann, M, Schober, H, Hansen, T
• Format: Journal Article
• Language: English
• Published: United States 01.04.2005
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.94.125506

We report elastic and inelastic neutron scattering experiments on different amorphous ice modifications. It is shown that an amorphous structure (HDA') indiscernible from the high-density phase (HDA), obtained by compression of crystalline ice, can be formed from the very high-density phase (vHDA) as an intermediate stage of the transition of vHDA into its low-density modification (LDA'). Both HDA and HDA' exhibit comparable small-angle scattering signals characterizing them as structures heterogeneous on a length scale of a few nanometers. The homogeneous structures are the initial and final transition stages vHDA and LDA', respectively. Despite their apparent structural identity on a local scale, HDA and HDA' differ in their transition kinetics explored by in situ experiments. The activation energy of the vHDA-to-LDA' transition is at least 20 kJ/mol higher than the activation energy of the HDA-to-LDA transition.