# How to analyse structure factors calculated from a mixture of isotropic amorphous substrates

I am looking for a way to computationally analyse the interactions between two molecular species (as solute and solvent) in an isotropic mixture using X-ray scattering. Is there a guideline as to how an obtained structure factor, $$S(q)$$, can be analysed?

As an example, Figure 2 (below) from Structural analysis of ionic liquids with symmetric and asymmetric fluorinated anions shows the $$S(q)$$ for various ionic liquids and suggests that the dashed vertical line at 2 $$Å^{−1}$$ is the approximate boundary between intermolecular ($$q < 2 Å^{−1}$$) and intramolecular ($$q > 2 Å^{−1}$$) interactions, which is not clearly evident from the article itself.

A radial distribution function (RDF) for a solid-liquid or liquid mixture can be analysed in terms of solvation shells, coordination numbers, etc, so I was hoping there might be a similar way we can analyse structure factors.

• Its seems like there are two distinct questions in the post. It would probably be better to have each of these as separate posts. It will make it easier for answerers if they only know one part and make it easier to find for people for info about either of the two problems.
– Tyberius
Aug 17 '21 at 2:52
• @Tyberius I gave the example of RDF so as to do a similar analysis for SWAXS spectra. Otherwise I am trying to ask almost the same problem with both questions.
– mykd
Aug 18 '21 at 21:08
• @mykd congrats on being awarded vox populi! Your posting of this question on Twitter has attracted some retweets and likes so far, though a lot of viewers won't know what it is that they're looking at without a bit more context, so I'm not sure how many clicks it's getting. The StackMatter page has a lot of good examples of how it's worked for other people. Aug 25 '21 at 20:00
• For example this one got 7 retweets. Aug 25 '21 at 20:00
• After delving more deeply into this, I agree with @Tyberius that the question "How can we analyse the SWAXS spectra in a similar manner to RDFs for solid-liquid mixtures in terms of solvation shells, coordination numbers, etc?" would be better asked as a separate question. The second question is specifically about SWAXS whereas the first question is for any structure factor S(q). Also, the second question is specifically asking about if SWAXS spectra can be analyzed in a way similar to RDFs whereas the first question allows for any type of analysis method, regardless of similarity to RDFs. Dec 31 '21 at 1:20