Louis Bosio

Structural study of water confined in porous glass by neutron scattering

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. ...

A neutron scattering study of liquid D2O under pressure and at various temperatures

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.

Structure of high‐density amorphous water. II. Neutron scattering study

High‐density amorphous water is studied by neutron scattering in a Q range extending to 16 A−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.

Ion channel containing mesophases: structural characteristics of condensed phases of crown-ether-substituted phthalocyanines

Abstract A copper complex of a phthalocyanine substituted with four benzo-15-crown-5 1,Cu and the corresponding dihydrogeno-derivative 1,H2 were synthesized. X-ray determinations at small angles permitted us to characterize two types of condensed phases. Solid phases with orthorhombic structure were found for 1,H2 and for 1,Cu (a=20.5, b= 18, c=4.2 A). In these forms, two-dimensional rectangular arrays of substituted phthalocyanines lead to corrugated planes. Phthalocyanine moieties are superposed in an eclipsed conformation and the crown-ether macrocycles form channels. Metastable mesophases could also be characterized by X-ray diffraction. In this case, only two broad lines at 20.8 and 8.2 A and two halos at 3.5 and 4.2 A are observed for 1,Cu. The dihydrogeno-derivative leads to a similar pattern but only one halo is noticed at 4.2 A. The mesophases are constituted of two-dimensional square lattices superposed in a staggered conformation.

X‐ray and neutron scattering studies of the structure of water at a hydrophobic surface

The structure of water in contact with a hydrophobic surface, namely, activated carbon, is studied using both x‐ray and neutron scattering techniques. The structure factors and the corresponding radial distribution functions are determined for several levels of hydration, at room temperature and down to 77 K. At high water content (∼200%), the properties of water are very similar to those of bulk water; in partially hydrated samples (<50%), the molecular structure exhibits change of its local environment within particular a distortion at the level of the second neighbors, and water does not crystallize when the temperature is lowered.

Structure of high‐density amorphous water. I. X‐ray diffraction study

X‐ray diffraction measurements up to momentum transfer q=16 A−1 were performed at atmospheric pressure on both the high‐density form of amorphous ice obtained by pressurization of crystalline ice Ih at 77 K up to 2 GPa and the low‐density form obtained by further heating. These two amorphous phases exhibit significant differences at the level of the second‐ and third‐nearest neighbors which involve a decrease of the O–O–O angle on compression at high pressure. Moreover, it is found that the low‐density form is quite similar to that obtained by vapor deposition on cooled substrates at 77 K.

Crystal structures of Ga(II) and Ga(III)

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 A and 12 atoms in the centered cell; Ga(III) has a body‐centered‐tetragonal cell with a=2.813±0.003 A, c=4.452±0.005 A, and two atoms (this phase was previously labeled as Ga(II) in works cited in the text).

X-ray and neutron scattering studies of the structure of hyperquenched glassy water

X‐ray and neutron diffraction measurements were performed on glassy water prepared by rapid cooling of water droplets on a cryoplate. Structure factors and radial distribution functions were found to be nearly identical to those obtained from amorphous ice formed either by vapor deposition onto substrates cooled at 77 K or after heating the high‐density amorphous ice.

X-ray and neutron scattering studies of the temperature and pressure dependence of the structure of liquid formamide

A structural investigation of liquid formamide was performed by neutron scattering at pressures of up to 4 kbar. We have also deduced the molecular pair correlation functions from x-ray studies at ambient pressure and in the 263–326 K temperature range. The spectra obtained are consistent with the presence of hydrogen-bonded open chains of molecules in the liquid state. The effect of both pressure and temperature on the hydrogen-bond network is examined.

X‐ray diffraction study of liquid mercury over temperature range 173 to 473 K

The structure of liquid mercury has been studied with both CuKα and MoKα radiation using a theta–theta diffractometer with monochromator in the diffracted beam. Special attention has been paid to the temperature dependence of the liquid structure and the use of small droplets of about 5 μm diameter actually allowed measurements on supercooled liquid down to 60 K below the normal melting point. No significant variation in the first coordination number is observed over the temperature range studied, the change in the shape and the height of the first peak of the structure factor being probably due to some long range correlation increase when the temperature is lowered. A structure model based on a relaxed lattice is found to fit satisfactorily the experimental pair correlation function for liquid mercury.