Re: 3D powder averaging...
Dear Jon, Considering the link you gave: http://www.buzzfeed.com/lukelewis/what-british-people-say-versus-what-they-mean I think it would be relevant to clarify your sentence: ‘Choosing to single out individual publications for public abuse on a mailing list is a bit of a shame’. I believe that public discussion of publications is absolutely normal in any media provided the discussion is open, honest and reasoned enough. So, your term ‘public abuse’ is probably related to emotional comments without reasons and arguments. Best regards, Leonid ***Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660036, Akademgorodok 50/24, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid *** - Original Message - From: Jonathan Wright wri...@esrf.fr To: Alan Hewat alan.he...@neutronoptics.com Cc: rietveld_l@ill.fr Sent: Monday, May 11, 2015 1:56 AM Subject: 3D powder averaging... On 2015-05-10 17:36, Alan Hewat wrote: Jon... nicely illustrated... by posting an interesting link... Thanks! Obviously I think these serial methods are a fantastic opportunity for this community. An IUCrJ commentary by me is here: Serial crystallography for the masses: http://journals.iucr.org/m/issues/2015/01/00/hi0136/index.html ...which is all about a paper showing that unbelievably weak and noisy data can be merged into a 3D dataset. An open question is: will the new community of people developing these 3D methods ever show up on this list? In principle Rietveld methods and powder experts should have a lot to offer, but until now it seems to be mostly protein crystallographers who are getting the beamtime at the FEL. Would point-by-point Rietveld refinement extend to scaling and fitting all the snapshots? The profile function comes in as where you think each intensity was on the rocking curve. Actually I think Jon was being a little snarky himself. ... Not entirely*, if I wanted to 'wind you up' I'd have linked something from electron microscopy :-) This one just came out: http://news.sciencemag.org/biology/2015/05/electron-microscopes-close-imaging-individual-atoms Obviously powder diffraction has a rich and exciting future, especially when it is used as an imaging method. Google finds this one for Rietveld tomography: J. Appl. Cryst. (2011). 44, -1119[ doi:10.1107/S0021889811024423 ] Hard X-ray diffraction scanning tomography with sub-micrometre spatial resolution: application to an annealed [gamma]-U0.85Mo0.15 particle H. Palancher, R. Tucoulou, P. Bleuet, A. Bonnin, E. Welcomme and P. Cloetens There are always exciting future directions. Doubtless others will respond with what is new and exciting with neutrons and PDF's, etc. (yes, that is a challenge). Choosing to single out individual publications for public abuse on a mailing list is a bit of a shame. If you write a comment on the authors get a fair chance to respond (and privately tear you apart if you're wrong). If your comment survives then future readers of the paper will be informed, which does not happen when something is posted here. Highlighting things which _are_ worth reading is something I always appreciated from Armel's contributions to the list over the years. All the best, Jon === * http://www.buzzfeed.com/lukelewis/what-british-people-say-versus-what-they-mean ++ 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/ ++
Re: 3D powder averaging...
There is, of course, the Neutron Mailing List, which you can subscribe to at http://neutronsources.org/mailman/listinfo/neutron. It has a very different character to this list. It is mostly a vehicle for making announcements about conferences, job positions, proposal calls, etc. We did experiment with a parallel list that was designed for the kinds of discussions that this list contains, but it generated so little traffic that we shut it down. It might have been bad timing or inadequate promotion, but I suspect that you have to have a fairly focussed topic supported, nevertheless, by a large expert community to be as successful as the Rietveld list is. It would certainly be possible for neutronsources.orghttp://neutronsources.org to host other lists, perhaps even one that promotes joint neutron/x-ray experiments. Ray On May 11, 2015, at 1:45 AM, Julian Richard Tolchard julianrichard.tolch...@sintef.nomailto:julianrichard.tolch...@sintef.no wrote: Is there perhaps a case for extending the scope of the mailing list? I'm sure many of us are active with non-Rietveld methods of analysing x-ray and neutron scattering data. Perhaps the list could expand accordingly and become something like the X-ray and Neutron Scattering mailing list? jools From: alan.he...@gmail.commailto:alan.he...@gmail.com [mailto:alan.he...@gmail.com] On Behalf Of Alan Hewat Sent: 10. mai 2015 23:26 To: Jonathan Wright Cc: rietveld_l@ill.frmailto:rietveld_l@ill.fr Subject: Re: 3D powder averaging... ... Doubtless others will respond with what is new and exciting with neutrons and PDF's, etc. (yes, that is a challenge). With the greatest respect, It is not always the new and exciting techniques that produce the best science. Certainly using imaging methods for powder diffraction is promising, but it would be brave to propose already that it will have an impact comparable to that of the Rietveld method. I hear what you say, and what has been achieved so far is quite good, but I would suggest that we wait a little before drawing conclusions. ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.commailto:alan.he...@neutronoptics.com Send commands to lists...@ill.frmailto: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/ ++ -- Ray Osborn, Senior Scientist Materials Science Division Argonne National Laboratory Argonne, IL 60439, USA Phone: +1 (630) 252-9011 Email: rosb...@anl.govmailto:rosb...@anl.gov ++ 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/ ++
This and that
Alan, the latest thread on Rietveld and powder diffraction has been most interesting and even thought-provoking. So you should be encouraged to continue with this group. I read it regularly and value it a lot. Some particular comments, if I may: 1. Your point about all structures being triclinic: yes that may be true, but most of what we want to find out about in terms of structure is the average, and that is where one uses higher symmetry as an aid to getting an acceptable solution. 2. Having said that, when I started in this Rietveld business (your fault if you recall!) we accepted that long-range periodicity was what we assumed and that crystal structures for the most part were regular (remember early papers of yours and mine!). However, over the years it has become increasingly clear that it is the departures from regularity that we need to study more. In my own research the gradual realization of this in the PZT series is an example (see http://www.nature.com/ncomms/2014/141024/ncomms6231/abs/ncomms6231.html). In this case, it has become clearer (or at least I think so) that real systems like this are far more complex than thought hitherto. In PZT we now have evidence that the true structure is monoclinic rather than rhombohedral (yes you can call it triclinic if you want but that just introduces too many parameters to be useful), at the unit cell level, but averages into large scale regions that are on average rhombohedral and those that are monoclinic i.e. a mixture of different coherence regions. This was achieved by a combination of neutron Rietveld and PDF. Similar complexities are beginning to be found elsewhere (in the perovskite field for sure). 3. The future? Always dangerous to make predictions (much greater scientists than I have fallen into that trap). In the long run I suspect that the need for crystals in the molecular sciences will become unnecessary. For the most part molecular crystallographers only use crystals as a means of ordering individual molecules so that they can be used in diffraction. They are interested in the molecules and the crystal structures (packing, intermolecular contacts) are of no interest. This is especially the case for macromolecular people for whom having to crystallise molecules is a pain. On the other hand, much of inorganic and related materials have properties that depend on the crystal structures, and so crystals will remain of importance. It may well be the case that the need to do actual powder diffraction for structural studies though will largely go, as techniques evolve to enable individual crystallites to be studied. I guess it will remain necessary though for phase identification studies. Who knows? Except that the whole field of crystallography is undergoing major development right now with the brilliant new techniques appearing in EM, synchrotrons, FEL's, neutron sources, NMR, Raman etc etc. It is in fact an exciting time for crystallography. Mike Glazer ++ 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/ ++
RE: Apologies... The No Attachment rule.
After reading the slew of emails that landed in my inbox over the last couple of days I'll put my hat on as CPD chair and put my head above the parapet (hopefully not to be shot at) The IUCr (and others) have tried to get journals to use powder cifs and checkcif for structures for some time with limited success. The powder CIF is less than ideal we know but it does work (with some frustrations). This doesn't stop lousy data being used in papers for other purposes but we have to trust to the admittedly imperfect peer review process to weed out the worst offenders. Education in powder diffraction (or the lack of) is an ongoing problem but resources do exist if you search for them. I believe I mentioned these in the past but no harm repeating the point The CPD webpage has a number, including the Erice school content which covers alot of advanced material and the Canadian Powder Diffraction workshop which has more basic material. http://www.iucr.org/resources/commissions/powder-diffraction/schools The Rietveld refinement guidelines are an oft-ignored resource which is now open-source so no excuse not to read them (and hopefully heed their recommendations) http://dx.doi.org/10.1107/S0021889898009856 Pam From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of Lubomir Smrcok [uachs...@savba.sk] Sent: Sunday, May 10, 2015 3:25 PM To: Kurt Leinenweber Cc: rietveld_l@ill.fr Subject: RE: Apologies... The No Attachment rule. Hi Rievelders, Although I have gone in the past years a long away from daily rietvelding, from time to time I can't resist my temptation to comment on some posts (OK, if the cap fits ... :-) and some of the comments could be well called snarky. But if you read that someone i) in facts asks people to solve his problem ASAP, or ii) a beginner without knowledge of elementary crystallography tries to refine ADP of a cubic special position, because a SW permits and complains about matrix problems, or iii) someone attempts quantitative standardless phase analysis of mixtures of disordered minerals whose structures are at maximum just estimated ... etc., etc.. All right, you may accuse me of going too far, or of exaggerating but isn't it at least half true ? If it is a PhD student I always ask where's his/her supervisor ? We could also ask the companies who claim that perfect (and I simply must add here : though physically or statistically impossible - not to speak of common sense ... ) results can be easily achieved when their SW is applied. Should we tell them or better not as are we afraid ( I am not, I do not apply :-) of loosing their sponsorships ? Best, Lubo On Sun, 10 May 2015, Kurt Leinenweber wrote: Hi, The subject of snarky comments is a fascinating one. I have definitely been the recipient of snarky comments for some of my more stupid posts on this list. The good thing about them is that it lets you know that you are saying or doing something, crystallographically speaking, that is really unpalatable to someone out there, and you might need to know this for your own good. I have definitely been chastised and have learned some things over the years by being forced to read a snarky response to one of my posts. But on the other hand, to a beginner a snarky comment can be damaging. However, these comments are not confined to mailing lists ? they happen at conferences too and they are just part of the fabric of science. As long as the whole list does not descend into a chaos of snarky comments, I think it?s OK to let them get through. One possible remedy is for others to come to the defence of a victim of excessive snarkiness. I have seen that happen on this list sometimes, and other times have been tempted myself to intervene, though I usually have not been brave enough (especially when the snark source is someone famous). - Kurt From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Darren Broom Sent: Sunday, May 10, 2015 3:36 AM To: Alan Hewat; Leopoldo Suescun Cc: rietveld_l@ill.fr Subject: RE: Apologies... The No Attachment rule. Hi Alan Thanks for the explanation. The point about the archive seems to me to be the most persuasive - I see what you mean. Providing the file sharing links stay active that does ensure the archive remains useful without having to host additional files on the archive server. It does seem that removing any attachments automatically would be the best solution. Hopefully Song Zhen's suggestion will help sort that out. Incidentally, Jon nicely illustrated one of the things about the list that I really appreciate, by posting an interesting link that I hadn't seen before and probably wouldn't have come across otherwise. Also, I wondered if you could set up SYMPA so that it strips emails of any unnecessary snarkiness (above a predefined threshold)? Best regards, Darren
