Thanks Mathew, for the summary of the replies you received off-list. Just a remark to those who reply off-list. The purpose of the Rietveld list is to facilitate discussion. That can't happen if the conversation is off-list.
Alan ________________________________ Dr Alan Hewat, NeutronOptics Grenoble, FRANCE (from phone) alan.he...@neutronoptics.com +33.476984168 VAT:FR79499450856 http://NeutronOptics.com/hewat _______________________________ On Wed, 13 Apr 2022, 07:01 Matthew Rowles, <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: image.png] > This is using the scattering factors defined with 11 gaussians. > > If you use the ones defined by 9 gaussians, you get > [image: 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 12 x 0 y 0 z 0.14772 occ Al+3 1. beq 0.318 > site O1 num_posns 18 x 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 6 x 0.0806 y 0.5095 z 0.3020 occ Si+4 1 beq 0.25 > site Si2 num_posns 6 x 0.1675 y 0.2560 z 0.0070 occ Si+4 1 beq 0.29 > site N1 num_posns 2 x 0 y 0 z 0 occ N 1. beq 0.88 > site N2 num_posns 2 x =1/3; y =2/3; z 0.3500 occ N 1. beq 0.46 > site N3 num_posns 6 x 0.0390 y 0.3860 z 0.0310 occ N 1. beq 1.06 > site N4 num_posns 6 x 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 6 x 0.2323 y 0.4096 z 0.25 occ Si+4 1 beq 0.231 > site N1 num_posns 2 x =1/3; y =2/3; z 0.25 occ N 1 beq 0.326 > site N2 num_posns 6 x 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> 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_al656.xy >> >> >> Thanks >> >> Matthew >> >> >> >> >> >> On Wed, 16 Mar 2022 at 21:13, Matthew Rowles <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/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >
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