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
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.w...@qut.edu.au | Web: www.qut.edu.au/ife/carf
At 2022-04-13 13:00:44, "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:
This is using the scattering factors defined with 11 gaussians.
If you use the ones defined by 9 gaussians, you get
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> 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
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