<div dir="ltr"><br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
From: Anjaiah Nalaparaju <<a href="mailto:anjai.che@gmail.com">anjai.che@gmail.com</a>><br>
<br>
My question is related to the unmerged patch for module waxsdebye.<br>
<br>
1. Can anybody tell the reference for the form factor<br>
coefficients(a1-a5,b1-b5,p1-p3) in file "sfactor_atom_nods_Fourier.xml" or<br>
all the new .xml files on sfactors. These number look very much different<br>
from the sfactor.dat which are cromer-mann coefficients.<br></blockquote><div>There is no reference (yet). The numbers are different because it's a different parametrization. Since solvent-corrected form factors have a more complex shape, we've used a short Fourier sum plus a polynomial, instead of gaussians. The form factor is calculated from these parameters in src/gromacs/waxsdebye/scattering_factors.cpp.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
2. If we use the following equation to calculate atomic form factors, at<br>
q=0 sum of co-eff a1 to a5 should be equal to the form factor value at q=0<br>
given in the publication "Niebling, Bj?rling and Westenhoff, J. Appl.<br>
Cryst. 47 (2014) 1190"<br></blockquote><div>No they shouldn't, there's also a polynomial there. Again, see scattering_factors.cpp. Have that code print out the scattering factors if you would like to test them.<br><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
[image: View the MathML source]<br>
<br>
But seems the coefficients in .xml files are not corresponding to this<br>
equation.<br>
<br>
3. How can the coefficients after displaced volume correction can be a<br>
constant value ( sfactor_atom_ds_Fourier.xml), as the displaced volume<br>
correction term also function of "q". "Svergun, Barberato and Koch, J Appl.<br>
Cryst. 27 (1995) 768."<br></blockquote><div>I'm not sure what you mean by "constant value". <br></div><div> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
3. Where the form-factors with displaced volume corrections are calculated <br>
in the code.<br></blockquote><div>The displaced volume corrections are not done in the code. The scattering factors with or without the correction (depending on which xml file is used) are calculated in scattering_factors.cpp.</div><div> <br></div></div></div></div>