Hi Jon The data is put on an absolute scale through the external standard approach. The calculations assume that the QPA for corundum in NIST SRSM676a is 99.02 wt%. This scaling factor is then applied to the silicon nitride pattern.
re surface roughness: The samples were backpacked against a glass surface, and the powders used as-received. I've never measured the particle size distribution of either (any!) SRM, but the certificates describe 676a as "fully disaggregated" and "grains are sub-micrometer in size and equi-axial in shape" and the 656 certificate has a particle size distribution by laser scattering, with 100% less than 5 um. In our other work, we aim to micronise to less than 10 um. Our grinding checks show that we get 100 vol% <15 um and 95 vol% <6 um. I've never used the Pitschke or Suortti roughness corrections available in Topas, and have no intuition as to the magnitude of their correction or what "proper" values should be. Matthew On Wed, 13 Apr 2022 at 18:11, Jonathan WRIGHT <wri...@esrf.fr> wrote: > Maybe a silly question: are you assuming you have the data on an absolute > scale > in order to do these calculations? Do things like surface roughness > somehow not > matter? > > Best > > Jon > > > > > On 13/04/2022 11:56, Matthew Rowles wrote: > > Thanks Tony > > > > When I add the absorption edge correction to the silicon nitride model > (and add > > beta-silicon nitride), it becomes -2.8 wt% amorphous; up a little due to > the > > added correction and down a little due to the extra phase. > > > > If I change your al-SN thermals from 1 to those given in ICSD 77811, I > get +4.8 > > wt% amorphous. Your atoms were already neutral, so I left them as-is. > > > > If I make all the Si-nitride phases' thermal parameters == 0, then I can > get up > > to 8.5 wt% amorphous. > > > > In all of this, corundum is staying as charged atoms, with Al and O beqs > fixed > > at 0.334 and 0.278. > > > > I'll have to have a go at applying the absorption edge correction; I > always > > forget which parameter is which thing and have to rederive my > understanding of > > it everytime... > > > > > > Thanks > > > > Matthew > > > > On Wed, 13 Apr 2022 at 13:58, iangie <ian...@126.com <mailto: > ian...@126.com>> wrote: > > > > Dear Matthew, > > > > I tried your data and get ~-1% amorphous. My .pro is in below link. > > > > https://www.dropbox.com/s/xuw13c91l9gq5m5/ROW.pro?dl=0 > > <https://www.dropbox.com/s/xuw13c91l9gq5m5/ROW.pro?dl=0> > > > > I normally do not refine Beq, which I believe gives biggest source > of error > > in QPA... > > > > > > Cheers! > > > > -- > > > > *Dr. Xiaodong (Tony) Wang* > > *Senior Research Infrastructure Specialist (XRD)* > > Central Analytical Research Facility (CARF) | Queensland > University of > > Technology > > *Address:* Level 6, P Block, Gardens Point campus, 2 George St > Brisbane QLD 4000 > > *Tel:*+61 7 3138 1904 | *Mob:*0452 571 680 > > *Email:* tony <mailto:stephen.blank...@qut.edu.au>. > > <mailto:stephen.blank...@qut.edu.au>w...@qut.edu.au > > <mailto:stephen.blank...@qut.edu.au> | *Web:* > www.qut.edu.au/ife/carf > > <http://www.qut.edu.au/ife/carf> > > > > > > At 2022-04-13 13:00:44, "Matthew Rowles" <rowle...@gmail.com > > <mailto:rowle...@gmail.com>> wrote: > > > > Hi all > > > > Thanks to those that have replied off-list. > > > > I've managed to jiggle things around and get various answers. If > you > > want an answer between -14 and +6 wt% amorphous, I can make it > happen. I > > can either use charged atoms or not, or use thermal parameters > or not. > > Combining those between the corundum and Si3N4, you get the > following: > > > > > > image.png > > This is using the scattering factors defined with 11 gaussians. > > > > If you use the ones defined by 9 gaussians, you get > > image.png > > > > The structures I used are below. In the certificate for 656, the > > structures are referenced, but those structures have no thermal > > parameters. Does anyone know what was used in the NIST > determination? > > > > > > > > phase_name "Aluminium_oxide_alpha_10425_icsd" > > Hexagonal( 4.759355, 12.99231) > > space_group "R -3 c H" > > site Al1 num_posns 12x 0 y 0 z 0.14772 occ Al+3 1. beq > 0.318 > > site O1 num_posns 18x 0.3064 y 0 z 0.25 occ O-2 1. beq > 0.334 > > > > phase_name "ALPHA_Marchand_ICSD_26191" > > Hexagonal( 7.75411, 5.62034) > > space_group "P31c" 'atom positions from Marchand. Thermals from > ICSD 77811 > > site Si1 num_posns 6x 0.0806 y 0.5095 z 0.3020 occ Si+4 1 beq > 0.25 > > site Si2 num_posns 6x 0.1675 y 0.2560 z 0.0070 occ Si+4 1 beq > 0.29 > > site N1 num_posns 2x 0 y 0 z 0 occ N 1. beq > 0.88 > > site N2 num_posns 2x =1/3; y =2/3; z 0.3500 occ N 1. beq > 0.46 > > site N3 num_posns 6x 0.0390 y 0.3860 z 0.0310 occ N 1. beq > 1.06 > > site N4 num_posns 6x 0.3190 y 0.3210 z 0.2660 occ N 1. beq > 0.17 > > > > phase_name "BETA_Billy_ICSD_35566" > > Hexagonal( 7.60633, 2.90778) > > space_group "P 63/m" ' structure from Billy, thermals from ICSD > 170004 > > site Si1 num_posns 6x 0.2323 y 0.4096 z 0.25 occ Si+4 1 beq > 0.231 > > site N1 num_posns 2x =1/3; y =2/3; z 0.25 occ N 1 beq > 0.326 > > site N2 num_posns 6x 0.3337 y 0.0323 z 0.25 occ N 1 beq > 0.314 > > > > > > > > > > > > > > On Tue, 12 Apr 2022 at 17:13, Matthew Rowles <rowle...@gmail.com > > <mailto:rowle...@gmail.com>> wrote: > > > > Hi all > > > > I've collected some more data, and am still getting spurious > > results, and by spurious, I mean -5 wt% amorphous in > SRM-alpha-656 > > when quantified by the external method against SRM 676a. > > > > We had some SRM-656alpha (couldn't find any of the > beta) stored in a > > drying oven, and some SRM676a stored in a cupboard. I > collected some > > data using a D8 with Ni-filtered Cu and a lynx-eye detector > (0.25° > > fixed divergence, 250 mm radius, 2x2.5° sollers). The > patterns were > > collected consecutively (using the same program), with a > single peak > > from SRM1976 (b, I think), acting as an intensity calibrant > (the > > intensity didn't appreciably change), collected before, > after, and > > between. > > > > Does anybody want to have a look at the data and see what > I'm doing > > wrong? Data available at: > > > https://raw.githubusercontent.com/rowlesmr/pdCIFplotter/changing-str-to-float-conversion/data/row_Cu_676a.xy > > < > https://raw.githubusercontent.com/rowlesmr/pdCIFplotter/changing-str-to-float-conversion/data/row_Cu_676a.xy > > > > > > > https://raw.githubusercontent.com/rowlesmr/pdCIFplotter/changing-str-to-float-conversion/data/row_Cu_al656.xy > > < > https://raw.githubusercontent.com/rowlesmr/pdCIFplotter/changing-str-to-float-conversion/data/row_Cu_al656.xy > > > > > > > > Thanks > > > > Matthew > > > > > > > > > > > > On Wed, 16 Mar 2022 at 21:13, Matthew Rowles < > rowle...@gmail.com > > <mailto:rowle...@gmail.com>> wrote: > > > > Hi List People > > > > Do any of you use NIST SRM656 in your quantitative > analysis > > quality control? > > > > I've recently started at a new lab, and am finding it > impossible > > to make a physically realistic model (in Topas) that > gives > > results anywhere near correct (or at least, close to the > > certificate values). > > > > As an example, using the external std approach with > SRM676, I've > > managed to calculate there is -11 wt% amorphous in the > beta-656 > > standard. > > > > I've tried using the silicon nitride structures given in > the SRM > > certificate, but the papers and the ICSD entries don't > list any > > thermal parameters. > > > > I can get the same results as given on the certificate > using a > > siroquant model, but I don't know the provenance of the > HKL > > files used in the analysis. > > > > > > Thanks in advance > > > > > > Matthew Rowles > > > > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 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://firstname.lastname@example.org/ > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 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://email@example.com/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >
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