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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 3106-3109 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6116-6125 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron diffraction with hydrogen/deuterium isotope substitution on the solvent water hydrogens is used to investigate changes in water structure around the apolar groups on alcohols and tetraalkylammonium ions at room temperature. The HH and HX correlations (where X is a nonsubstituted atom) are calculated for the following solutes in water: ethanol (5 mol%), tertiary butanol (3 mol%), tetrapropylammonium bromide (2.4 mol%), and tetrabutylammonium bromide (1.7 mol%). The correlation functions suggest that the water structure in all four systems is very similar to bulk water. There is no evidence of structural enhancement in going from pure water to water in the alcohol–water mixtures. There is a small but probably significant increase in structure in the tetraalkylammonium bromide solutions compared to both pure water and the alcohol–water mixtures. There is very little measurable difference between the two alcohol–water mixtures or the two tetraalkylammonium bromide solutions in terms of water structure. The results are consistent with the view that apolar solutes are located in cavities in the hydrogen-bonded water network, but they suggest that the increase in order associated with apolar hydration is a small effect in terms of structure.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6210-6215 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron diffraction studies are reported on H2O at temperatures of 300 and 400 °C. The method of isotopic substitution is applied to three mixtures of H2O and D2O, and the diffraction data are used to determine the three radial distribution functions gHH(r), gOH(r), and gOO(r). These results can be used to discuss changes in nearest neighbor structure between water molecules, and to assess the degree of usefulness of representative (usually pairwise) model potentials.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4123-4132 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron diffraction data on water, employing the technique of hydrogen/deuterium isotope substitution, are reported at three thermodynamic states above the boiling point. The structural information is analyzed in terms of the partial radial distribution functions, OO, OH, and HH, which are extracted from the neutron data. It is found that temperature affects mainly the medium and longer range order in the liquid, while density plays a significant role in controlling the degree of hydrogen bonding. To understand the structure of water obtained from these data it appears that many-body cooperative interactions have to be correctly accounted for.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 7650-7655 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron diffraction measurements on liquid ammonia at two temperature states on the liquid-vapor coexistence curve are presented. Three isotropic mixtures of hydrogenated and deuterated ammonia have been studied and the three radial atom–atom distribution functions extracted at 213 K and 273 K. The comparison of the experimental results with the partial radial distribution functions for orientationally uncorrelated molecules, shows some evidence for hydrogen bonding in liquid ammonia but this is much less pronounced than that found in water under ambient conditions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 7868-7872 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron diffraction isotopic substitution experiments on liquid n-decane (C10H22) and n-eicosane (C20H42) are described. The intermolecular H–H structure function hHH(Q) and the intermolecular H–H correlation function ginterHH(r) are obtained without recourse to models of the intramolecular structure. The structure of the ginterHH(r) found at 2.5, 5.0, and 7.0 A(ring) corresponds to different shells in the H–H pair correlation function. In addition, ginterHH(r)〈1 for a considerable range, due to the screening of intermolecular correlations by intramolecular correlations. This "correlation hole'' effect is accentuated by extrapolation of the structure functions to the expected infinite wavelength limit, and shows good agreement with values determined from small-angle neutron scattering (SANS) data. All of these features are in good agreement with the results of molecular dynamics simulations for the closely related system C13H28.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6888-6901 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recently it has been shown how the measured partial structure factors for diatomic molecular liquids might be used to generate a detailed view of the local intermolecular orientational correlation function, via the standard spherical harmonic expansion. The present work generalizes this analysis to the case of molecules of arbitrary shape. An analysis of the measured atom–atom partial structure factors for liquid water is presented, and the corresponding maps of the orientational correlation function between water molecules are derived. It is seen that this method of presenting diffraction data is rich in detail about the nature of the short-range interactions between water molecules in the liquid state. In particular, it is found that while there is a pronounced directionality in the organization of neighboring molecules around any given molecule at the origin, corresponding to the hydrogen bonding in the liquid, there are nonetheless a range of local orientations compatible with the neutron data. This argues against the notion of water forming short lived, "icelike'' clusters at ambient temperature and pressure, as has been speculated in the past. The general implications for this kind of analysis for other molecular liquids, solutions, and mixtures is discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5751-5760 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutron diffraction, in conjuction with substitution of deuterium (D) for hydrogen (H), has been used to determine the structure of interlayer water in sodium- and nickel-substituted vermiculites. We have measured the intensities of the (00l) Bragg reflections as a function of relative humidity and H/D content, up to l=30. Difference analysis has then been used to obtain separate density profiles, ρ(z), for both the hydrogen atoms and the oxygen atoms plus the clay sheets. Ni–vermiculite was studied at 84% relative humidity, while Na–vermiculite was studied at both 88% and 30% relative humidity. At these values the layer spacings are 14.40, 14.96, and 11.78 A(ring), respectively. We find that each interlayer nickel ion is coordinated octahedrally to 6.0 water molecules. All of these water molecules are oriented to form a strong hydrogen bond to the adjacent clay surface. We also find that extra water is located close to the clay layers. This additional water is situated within the hexagonal rings of SiO4 and AlO−4 tetrahedra, which comprise the clay surfaces. In the 14.96 A(ring) phase of Na–vermiculite there are an average of 4.9 interlayer water molecules per cation. About half of these water molecules are oriented to form a hydrogen bond to one of the clay surfaces. Additional water is found close to the clay surface, occupying the same hexagonal ring sites as in 14.40 A(ring) Ni–vermiculite. In the 11.78 A(ring) phase of Na–vermiculite there are an average of 2.1 water molecules per interlayer cation. The oxygen atoms of these interlayer water molecules are found close to halfway between the layers, while the hydrogen atoms are directed towards one of the adjacent clay sheets.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 8161-8168 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 942-945 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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