DOI: 10.5061/dryad.7sqv9s4wk
title: Experimental data for: Medium-density amorphous ice

description: Amorphous ices govern a range of cosmological processes and are
 potentially key materials for explaining the anomalies of liquid water. A
 substantial density gap between low-density amorphous (LDA) and the
 high-density amorphous ices (HDA) with liquid water in the middle is a
 cornerstone of our current understanding of water. However, we show that
 ball milling ‘ordinary’ ice Ih at low temperature gives a structurally
 distinct medium-density amorphous ice (MDA) within this density gap. These
 results raise the possibility that MDA is the true glassy state of liquid
 water or alternatively a heavily sheared crystalline state. Remarkably,
 the compression of MDA at low temperature leads to a sharp increase of its
 recrystallization enthalpy highlighting that H2O can be a high-energy
 geophysical material.
description: <strong>1.
 Low-temperature compression
 experiments</strong> MDA samples were transferred into indium gaskets
 located inside 8 mm-diameter harden-steel piston cylinders precooled with
 liquid nitrogen. Compression at 77 K for a range of pressures up to 1.6
 GPa was performed at 5 kN min<sup>-1</sup> using the
 computerized Zwick Roell Proline Z100TN Universal Testing Machine.
 Following decompression, the samples were recovered under liquid nitrogen
 for further analysis. In one experiment, a compressed sample was heated to
 250 K at ambient pressure to transform the sample to ice
 I<em>h</em> and then compressed again to 1.6 GPa at 77
 K.<br> <strong>2. Differential Scanning Calorimetry
 (DSC)</strong> Stainless-steel pans were filled with ice
 samples under liquid nitrogen and transferred into a pre-cooled
 PerkinElmer DSC 8000 advanced double-furnace differential scanning
 calorimeter. The samples were heated from 95 to 260 K at 10 K
 min<sup>-1</sup> and transformed to ice
 I<em>h</em>. A second scan from 95 to 260 K was then recorded
 and used as a background for the first scan. Finally, the amounts of
 H<sub>2</sub>O in the DSC pan were determined by recording the
 endothermic melting at 0°C and using 6012 J mol<sup>-1</sup>
 as the enthalpy of melting.
 <strong>3. X-ray
 diffraction measurements </strong> Ice samples were transferred into a
 purpose-built sample holder with Kapton windows under liquid nitrogen.
 Powder X-ray diffraction patterns were then recorded by mounting the
 sample holders on a Stoe Stadi P diffractometer with Ge 111 monochromated
 Cu Kα1 radiation at 40 kV and 30 mA, and a Mythen 1K area detector. The
 temperature of the samples was controlled with an Oxford Instruments
 Cryojet HT. <strong>4. Raman
 spectroscopy</strong> Raman spectra were recorded at 80 K using a
 Renishaw Ramascope (632.8 nm) and an Oxford Instruments
 Microstat<sup>N</sup> cryostat. <strong>5. Small-angle X-ray scattering
 (SAXS)</strong> <strong>
 </strong> Ball-milled ice samples were transferred into a
 self-built aluminum sample holder under liquid nitrogen. The sample holder
 consists of two 150 × 100 × 20 mm aluminum plates with a 4 mm-diameter
 bore in the center. One plate contains a 10 mm wide and 1.8 mm deep
 cylindrical recess with the bore in the middle which was covered with
 0.025 mm thick Kapton foil and filled with the ice sample. The second
 plate with Kapton foil covering the bore and a conical exit at the back
 was placed on top of the ice sample creating a closed 1.8 mm deep sample
 environment. The two plates were firmly held together by four M6 screws at
 the corners. A hollow 3D-printed base made from PLA was attached to the
 bottom of the two aluminum plates and a Pt100 temperature sensor was
 firmly inserted through a hole from the side of the aluminum block, close
 to the sample compartment, and secured with heat-conducting paste. The
 entire assembly was transferred quickly from liquid nitrogen into the
 vacuum chamber of a Ganesha 300XL SAXS instrument. After connecting the
 temperature sensor to a Lakeshore 331 cryogenic temperature controller,
 the vacuum chamber was evacuated to a base pressure of
 ~1×10<sup>-2</sup> mbar within a few minutes. A microfocus
 X-ray beam was generated with a copper source with a motorized collimation
 system of 2 sets of 4-blade single crystal slits. SAXS data was collected
 with a solid-state photon-counting detector (PILATUS 300 K, Dectris AG,
 Switzerland) mounted on a 1.4 m transverse rail along the beamline. SAXS
 data in the 0.15 to 0.7 Å<sup>-1</sup>
 <em>Q</em>-range with a resolution of 0.00179
 Å<sup>-1</sup> was continuously collected every 3 minutes from
 80 to 220 K over the course of about 10 hours. The measurements were
 repeated with an empty sample compartment but including the Kapton foils
 for background subtractions.
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