Bad quality mono is always possible. I've got kb coming through with a current instrument.
On Thu, 7 Sep 2023, 18:56 Reinhard Kleeberg, < kleeb...@mineral.tu-freiberg.de> wrote: > Hm, as Philips systems at this time always had combined a > scintillation counter with a diffracted beam graphite 002 bent > monochromator, the question arises how the W L series and Cu Kbeta > lines could reach the detector... Bad quality of the graphite mosaic > crystal? > > Reinhard > > Zitat von Le Bail Armel <le-bail.ar...@orange.fr>: > > > The muscovite data is dated 1996 from an old Philips 1710 diffractometer, > > > > vertical sample holder, scintillation counter, not much used because we > > > > had better instruments, hence this stupid test ;-) > > > > Armel > > > >> envoyé : 7 septembre 2023 à 10:57 > >> de : Reinhard Kleeberg <kleeb...@mineral.tu-freiberg.de> > >> à : rietveld_l@ill.fr > >> objet : Re: Step-like basline > >> > >> Dear Luca, > >> sorry, I don't understand the "mosaic crystal" eplanation, especially > >> not the "non-centre position" issue. IMHO, when the pattern was > >> measured at a "powder" Bragg-Brentano configuration, in reflection > >> mode, axial and equatorial divergence maximum ~ 2 degree, the 00l > >> series of all misoriented crystal blocks can fulfill the diffraction > >> condition only within the range of the instruments divergence, and the > >> parafocusing arrangement would reflect such blocks back very close to > >> the nominal angular position (as it is the case for a powder as well). > >> So single crystal reflection of big blocks should only be observable > >> within the total profile of a "normal" ideal powder peak (the > >> "instrumental" profile"). This is indeed what we see if coarsely > >> crystalline materials (e.g. quartz sand) are measured on a typical > >> powder diffractometer: Such peaks are extremely sharp, sometimes split > >> or doubled, sometimes with "wrong" alpha1/2 intensity ratio, or may > >> have small additional maxima and may be "edges" in their slopes, > >> depending on the number or size of crystals, but all these effects are > >> very close to the correct maximum position (+- <1 degree). So I can't > >> imagine that the unknown satellites in the mica pattern are > >> "misoriented-displaced" Cu Kalpha 00l peaks? > >> > >> Armel, what type of detector was used for this measurement? If the W L > >> series was detected, probably no diffracted beam monochromator, and no > >> Peltier cooled Si drift detector? If so, even more spectral > >> contamination may come into account. For example, I remember to have > >> complained about a new Co tube (no company names here) showing > >> systematic satellites ~ 1 % intensity from standard Si and LaB6 powder > >> measurements. The wavelength recalculated by Bragg's law was Zn Kalpha > >> (!!!), confirmed by spectral analysis, the tube Co target was > >> obviously contaminated. As the satellites in your example in the < 0.x > >> % magnitude of the Cu K alpha1 intensity, even quite low contamination > >> of other elements than W may be the source. So it could be > >> interesting to calculate wavelengths from all positions of the unknown > >> satellites for the d-spacings of the mica 00l series and see if any > >> calculated wavelengths do repeat. > >> > >> Another thought: > >> Here we have a single crystal of muscovite. As some of the unexplained > >> peaks appear to be extremely sharp, what about Renninger (multiple > >> diffraction) hkl peaks? Maybe there are enough lattice planes in the > >> monoclinic mica structure to give a chance for multiple diffraction to > >> get registered by a divergent beam (Bragg-Brentano) configuration? > >> Such peak positions appear to be unsystematic, with no relatiion to > >> the Cu Kalpha 00l. > >> > >> However, a take-home message of your example should be: Do never > >> measure single crystals in parafocusing geometry without safely > >> monochromatic radiation ;-) > >> > >> Best regards > >> > >> Reinhard > >> > >> Zitat von Luca Lutterotti <luca.luttero...@unitn.it>: > >> > >>> It is call graininess, as Miguel said before, these are mosaic > >>> single crystals and depending on your source (divergence, spot > >>> dimension at different angles etc.) you get each mosaic crystal to > >>> create a diffraction peak that especially at low two-theta angle may > >>> be displaced a lot from its theoretical position because it is > >>> diffracting from a non center position. This is what you get also > >>> when you analyse samples with extremely large grains. If you use a > >>> 2D detector instead of scanning with a point or small psd, you will > >>> see all these individual grain or mosaic crystals diffracting around > >>> their ideal spot or if it is a sample with just large grains, > >>> distributed around the Laue circle. More the grain is on a lateral > >>> position respect to the center of the beam, more it is displaced in > >>> two-theta. At higher angle your beam size on the sample is smaller > >>> and there is less displacement for geometrical reasons. > >>> I like to work with 2D detectors (texture, stresses) because it is > >>> easy to see these “figures”. > >>> In addition you have the spectral impurities identified by Frank and > >>> you may get some small grains with different orientation and twins > >>> that will create some of the non 00l peaks. > >>> Analysing these kind of patterns would require a sophisticated > >>> simulation of the grains-crystals distribution and computing like > >>> ray-tracing for the geometrical effects. Not worth it. Single > >>> crystals and sharp textures requires a point beam to avoid these > >>> effects. And a monochromatic one. > >>> > >>> Best regards, > >>> > >>> Luca > >>> > >>> <http://www.unitn.it/> > >>> > >>> Luca Lutterotti > >>> Dipartimento di Ingegneria Industriale > >>> Università di Trento > >>> via Sommarive, 9 - 38123 Trento (Italy) > >>> tel. +39 0461 2824-14 (Office), -34 (X-Ray lab) > >>> > >>>  > >>> > >>> Maud: http://maud.radiographema.com <http://maud.radiographema/> > >> > >>>> On 6 Sep 2023, at 17:43, Le Bail Armel <le-bail.ar...@orange.fr> > >>>> wrote:>> > >>>> Dear Frank, > >>>> > >>>> Same as you. I have not a complete solution. > >>>> > >>>> Best > >>>> > >>>> Armel > >>>> > >>>>> envoyé : 6 septembre 2023 à 16:57 > >>>>> de : Frank Girgsdies <girgs...@fhi-berlin.mpg.de > >>>>> <mailto:girgs...@fhi-berlin.mpg.de>> > >>>>> à : Le Bail Armel <le-bail.ar...@orange.fr > >>>>> <mailto:le-bail.ar...@orange.fr>> > >>>>> Cc: Rietveld_L <Rietveld_L@ill.fr <mailto:Rietveld_L@ill.fr>> > >>>>> objet : Re: Step-like basline > >>>>> > >>>>> > >>>>> Dear Armel, > >>>>> > >>>>> Thanks for this nice quiz! > >>>>> > >>>>> However, after identifying the following spectral impurities: > >>>>> Cu K_beta, > >>>>> W L_alpha1,2 > >>>>> W L_beta1,2,3,4 and > >>>>> W L_gamma1, > >>>>> I am stuck now, leaving bout 1/2 to 1/3 of the tiny extra peaks > >>>>> unexplained. > >>>>> > >>>>> Some of them look suspiciously like Cu K_alpha1+2 doublets and might > >>>>> thus belong to an impurity phase, or differently oriented > crystallites > >>>>> of the main phase, which could lie as dust on the single crystal > >>>>> surface, but I had no luck trying to identify them. > >>>>> > >>>>> Furthermore, the irregular high angle tailing of the 00l series > (maybe > >>>>> stacking faults?) makes peak fitting difficult. > >>>>> > >>>>> Thus, I give up (at least for now), hoping that you might disclose > the > >>>>> solution to the riddle, as far as it is known, for us after a while. > >>>>> > >>>>> Best wishes, > >>>>> Frank > >>>>> > >>>>> > >>>>> > >>>>> On 06.09.2023 10:47, Le Bail Armel wrote: > >>>>> > >>>>>> Hi, > >>>>>> > >>>>>> In the same subject. > >>>>>> > >>>>>> A special "powder pattern" to play with (try to explain all peaks) : > >>>>>> > >>>>>> http://cristal.org/muscovite.pdf <http://cristal.org/muscovite.pdf> > >>>>>> > >>>>>> Best > >>>>>> > >>>>>> Armel > >>>>>> > >>>>>> > >>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >>>>>> 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/ > >>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >>>>>> > >>>>> > > >>>>> > >>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >>>> Please do NOT attach files to the whole list > >>>> <alan.he...@neutronoptics.com <mailto:alan.he...@neutronoptics.com>> > >>>> Send commands to <lists...@ill.fr <mailto: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/ > >>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >> > >> -- > >> TU Bergakademie Freiberg > >> Dr. R. Kleeberg > >> Mineralogisches Labor > >> Brennhausgasse 14 > >> D-09596 Freiberg > >> > >> Tel. ++49 (0) 3731-39-3244 > >> Fax. ++49 (0) 3731-39-3129 > >> > >> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >> 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/ > >> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > -- > TU Bergakademie Freiberg > Dr. R. Kleeberg > Mineralogisches Labor > Brennhausgasse 14 > D-09596 Freiberg > > Tel. ++49 (0) 3731-39-3244 > Fax. ++49 (0) 3731-39-3129 > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 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/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >
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