Hi Lubo, if we speak of diffraction, we have a Fourier transformation, so we are not 100% in the direct space with any structure solution method.
However, the "structure solution in direct space" does not attempt to work in the reciprocal space - all the manipulations are done in the direct space. Also, it does not attempt to address properly the phase problem, which is defined in the reciprocal space, but is simply trying to find a model "directly" in the direct space. There is even no inverse FT calculated! So, it is the fair name, IMHO. Best regards, Yaroslav Wednesday, December 16, 2015, 11:05:05 PM, you wrote: > Hi, > I feel I have a problem with terminology. What's the right nickname for > the method of structure solution from powders, which instead of analyzing > electron (nuclear) density shuffles atoms or molecules around a cell and > compares experimental and calculated patterns ? It could be well used also > for single crystal data, I know, but it is not routinely done (yet ?). > I remember that colloquially used phrase "structure solution in direct > space" woke me up several times during plenary lectures at several > conferences. What are we having in direct space ? IMHO just electron > (nuclear) density. Its FT is our diffractogram so that if we fit > diffractogram, are we still in direct space ? Of course, reciprocal space > is a pure math and diffracted beam is quite realistic (BTW, are > there photons also in reciprocal space :-) ?). But in which space are we when > doing any > crystallographic calculation ? OK, OK, you know what I am asking ... no > bad jokes, please. > May I ask for your 2 cents ? > Thanks, > Lubo
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
