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
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