How about "reciprocal methods" as opposite to "direct methods" which work in reciprocal space? Peter
______________________________________ Peter Zavalij Director, X-ray Crystallographic Center University of Maryland, College Park, MD 20742 http:/www.chem.umd.edu/crystallography -----Original Message----- From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of ian.mad...@csiro.au Sent: Wednesday, December 16, 2015 6:29 PM To: yaroslav.filinc...@uclouvain.be; uachs...@savba.sk Cc: rietveld_l@ill.fr Subject: RE: structure solution terminology Hhmmm. A method which uses a model to calculate a diffraction pattern which is compared with observed data and the difference minimised by refining some parameters. Then restarting the process by randomly shuffling some parameters. I propose RRWAS - Rietveld Refinement With Atom Shuffling. Or maybe this is what you would define as a "bad joke". Cheers o----------------------------oo0oo----------------------------o Ian Madsen Honorary Fellow CSIRO Mineral Resources Flagship Private Bag 10, Clayton South 3169 Victoria, AUSTRALIA Phone +61 3 9545 8785 direct +61 3 9545 8500 switch +61 (0) 417 554 935 mobile FAX +61 3 9562 8919 Email ian.mad...@csiro.au o----------------------------oo0oo----------------------------o ________________________________________ From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of Yaroslav Filinchuk UCL [yaroslav.filinc...@uclouvain.be] Sent: Thursday, December 17, 2015 9:17 AM To: Lubomir Smrcok Cc: rietveld_l@ill.fr Subject: Re: structure solution terminology 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
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