Hi Ed The beam is smaller than the sample over all angles. - 0.25° divergence at 250 mm radius. I also collected in constant divergence mode, so the diffracting volume is a constant.
Matthew On Fri, 15 Apr 2022 at 01:20, Edward Laitila <ealai...@mtu.edu> wrote: > Just curious, is the sample as prepared in the holder wider than the beam > width at 10 degrees where you start the scan? This is a common issue that > not many realize that for quantitative analysis the diffracting volume is > constant provided the sample is larger than the beam in the tube and > detector plane. If the beam is larger than the sample at these > angles you no longer have a constant diffracting volume and hence errors in > the analysis. I am not sure many of the manufactures realize this based on > personal experience with default settings of optics for some > instruments being much too large. Additionally, background is a major issue > as I have found especially with amorphous materials present background > algorithms do not do a very good job and often create the background by > hand. > > Regards, > Ed > > On Tue, Apr 12, 2022 at 5:14 AM 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://www.mail-archive.com/rietveld_l@ill.fr/ >> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> >> > > -- > Dr. Edward A. Laitila > Senior Research Engineer/Scientist II/Adjunct Assistant Professor > Michigan Technological University > Dept. of MSE > Room 628 M&M Building > (906) 369-2041 >
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 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/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
