Diffusive dynamics during the high-to-low density transition in amorphous ice
- Stockholm Univ., Stockholm (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Stockholm Univ., Stockholm (Sweden)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hamburg Centre for Ultrafast Imaging, Hamburg (Germany)
- Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
- KTH Royal Institute of Technology, Stockholm (Sweden)
- Univ. of Innsbruck, Innsbruck (Austria)
- Argonne National Lab. (ANL), Argonne, IL (United States)
Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. In conclusion, the diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- AC02-76SF00515; 667205; 2013-3737-VR; P2ZHP2 148666; I1392; EXC1074; AC02-06CH11357
- OSTI ID:
- 1390292
- Alternate ID(s):
- OSTI ID: 1393142
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America, Vol. 114, Issue 31; ISSN 0027-8424
- Publisher:
- National Academy of Sciences, Washington, DC (United States)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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