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Using isotope substitution neutron scattering data, we present a detailed structural analysis of the short and intermediate range structures of the five known forms of amorphous ice. Two of the lower density forms—amorphous solid water and hyperquenched glassy water—have a structure very similar to each other and to low density amorphous ice, a structure which closely resembles a disordered, tetrahedrally coordinated, fully hydrogen bonded network. High density and very high density amorphous ices retain this tetrahedral organization at short range, but show significant differences beyond about 3.1 Å from a typical water oxygen. The first diffraction peak in all structures is seen to be solely a function of the intermolecular organization. The short range connectivity in the two higher density forms is more homogeneous, while the hydrogen site disorder in these forms is greater. The low Q behavior of the structure factors indicates no significant density or concentration fluctuations over the length scale probed. We conclude that these three latter forms of ice are structurally distinct. Finally, the x-ray structure factors for all five amorphous systems are calculated for comparison with other studies. [ABSTRACT FROM AUTHOR]

Detailed structural studies using powder neutron diffraction have been carried out on ices III and IX on both under-pressure and recovered samples. The incomplete hydrogen ordering in recovered ice IX first observed by La Placa et al. is confirmed, and our studies suggest similar orderings for the under-pressure and recovered phases. Sample history was observed to influence the lattice constants of ice IX, an effect which could relate to hydrogen ordering. There is an indication that ice III is not fully disordered, a conclusion which would be consistent with independent thermodynamic measurements. [ABSTRACT FROM AUTHOR]