In order to study the structural properties of water at interfaces, we performed neutron scattering experiments of water confined inside interconnected pores of Vycor glass. The structure factors and the corresponding radial distribution functions of the confined water have been determined as a function of temperature from 35°C down to -100 °C and for two levels of hydration of the glass (full and partial hydration). At 27°C, the structure factor of confined water is very similar to that of bulk water. When decreasing the temperature, we show that it is possible to supercool water inside pores of Vycor but not to the extent expected for such a small confining space. In fact the presence of large hydrophilic silica interface enhances the nucleation of ice. The observed phase of ice is the cubic ice which appears at about -18°C in the full hydrated Vycor. The other interesting observation is a greater degree of supercooling of water in partially hydrated samples of Vycor compared to fully hydrated ones. Moreover, the presence of a small amount of liquid water down to -40°C is identified.
The crystal structures of the high pressure Ga(II) and Ga(III) forms of gallium were studied by single-crystal x-ray diffraction using a diamond anvil device. Ga(II) has a body-centered-cubic structure with a=5.951±0.005 Å and 12 atoms in the centered cell; Ga(III) has a body-centered-tetragonal cell with a=2.813±0.003 Å, c=4.452±0.005 Å, and two atoms (this phase was previously labeled as Ga(II) in works cited in the text).
A structural investigation of liquid D2O was performed by neutron scattering at pressures up to 6 kbar and in a range of temperatures from 53 down to −65 °C. Some comparison is made with Monte Carlo (MC) and molecular dynamics (MD) simulations. In particular, the results are used to test some recent MD simulations leading to a phase diagram which provides a complete picture of the stable and metastable behavior of water and incorporates the two amorphous ices of water.
High-density amorphous water is studied by neutron scattering in a Q range extending to 16 Å−1. The low density form of amorphous water is also analyzed and compared with previous results. There are very important differences in the composite pair correlation functions of the two forms of amorphous ice, in particular beyond the first nearest-neighbors distance. We conclude that the hydrogen bond network is strongly deformed in a manner analogous to that found in water at high temperature. This is in contrast with the behavior of the pair correlation function of low-density amorphous water, which is closer to that of supercooled water.
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