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Can someone explain in layman's term how this figure shows the presence of Cl and Li ions in Ice VII ?

What can we deduce about the crystal from this data ?

enter image description here

enter image description here

The whole figure and caption are available here :

http://www.nature.com/nmat/journal/v8/n5/fig_tab/nmat2422_F1.html#figure-title

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    $\begingroup$ Can't find those B factors, but Q is clearly the magnitude of the wave-vector. $\endgroup$
    – valerio
    May 23, 2016 at 12:32
  • $\begingroup$ Do you know how to interpret this figure ? I don't understand the link with the structure of the crystal and the presence or not of particular species. $\endgroup$
    – mwa1
    May 23, 2016 at 12:40
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    $\begingroup$ I read the first part of the article. If I am correct, they don't want to show that Cl and Li ions are present - they know that they are. They want to show that the structure of the crystal they obtained is that of ice VII. Quoting: "In the course of our measurements, we discovered that glassy LiCl·6D2O crystallizes under pressure in a new and unexpectedly simple salt hydrate, which can be regarded as an ‘alloyed’ high-pressure ice phase [...] we found here by high-pressure neutron diffraction is a salt hydrate based on ice VII" $\endgroup$
    – valerio
    May 24, 2016 at 22:27
  • $\begingroup$ They also talk about "Huang scattering" being a " fingerprint for incorporation of Li and Cl into the ice VII structure". I can't seem to find much information on Huang scattering and it is probably too advanced for me anyway. But maybe you're right and the figure is mostly showing that the structure is that of ice VII. $\endgroup$
    – mwa1
    May 25, 2016 at 9:32
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    $\begingroup$ But you're right, in the second page they write "The observation of Huang scattering, the unusually strong attenuation of Bragg reflections and the expanded lattice parameters conclusively suggest that the Li and Cl ions are incorporated into the ice VII structure, rather than being expelled into grain boundaries." The $Q$ of the sharp peak should correspond to the reciprocal lattice spacing, from which you can obtain the lattice parameter. Don't really know about the other two features... $\endgroup$
    – valerio
    May 25, 2016 at 10:31

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