iFit/sqw_powder

 data = sqw_powder(model, p, q, w) : evaluate a 4D S(hkl,w) model/data set into a 2D S(|q|,w) data set for e.g. powders

   iFunc/sqw_powder:
     The conversion between rlu (in the model) and Angs-1 in the S(q,w) powder data set
     is done using the B=[a* b* c*] matrix. It is searched as 
     UserData.atoms.reciprocal_cell when using an input iFunc object, 
     and 'reciprocal_cell' when using an input iData object.
     

 input:
  model: a 4D S(q,w) model or data set (iFunc/iData)
  p:     model parameters, or left empty (vector)
  q:     wavevector values in Angs-1 (vector)
  w:     energy values in meV (vector)
 output: 
  data:  a S(|q|,w) data set or 2D Model

 example:
  s=sqw_phonons([ ifitpath 'Data/POSCAR_Al'],'metal','EMT');
  pow=sqw_powder(s); % then plot [q=0:2 w=0:50]
  plot(log(iData(pow,[],linspace(0,2,30),linspace(0,50,51))))

 Version: Aug. 22, 2017
 See also iData, iFunc/fits, iFunc/plot, gauss, sqw_phonons, sqw_cubic_monoatomic, sqw_vaks
   <a href="matlab:doc(iFunc,'Models')">iFunc:Models</a>
 (c) E.Farhi, ILL. License: EUPL.