<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
mso-margin-top-alt:auto;
margin-right:0cm;
mso-margin-bottom-alt:auto;
margin-left:0cm;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 2.0cm 2.0cm 2.0cm;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Thank you to ALL who have replied,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I forward here the main answers, so that some future GSAS-II user browsing the mail archive can find some info and does not need to bother you again for the same
things.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Instead, I will probably bother you again for different things,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Kind regards,
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Arianna Lanza<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Nick Weadock [mailto:nweadock@gmail.com]
<br>
<b>Sent:</b> martedì 27 febbraio 2018 19:39<br>
<b>To:</b> gsas-ii@aps.anl.gov; Arianna Lanza <Arianna.Lanza@iit.it><br>
<b>Subject:</b> Re: GSAS-II Digest, Vol 162, Issue 1<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">Hi Arianna,<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">The instrument broadening parameters are unique to each instrument. There was a paper published that looks at a few common instruments (Kaduk, J. and Reid, J. Powder Diffraction 26 (1) 2011, 88-93) and reports U,V,W,X,Y, asym, S/L, H/L,
etc. These may be a good guideline, but your instrument should really be calibrated with a SRM. <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">I had a similar result to you on my instrument when refining the instrument parameters using LaB6 SRM. I achieved better fits refining first X and Y, then UVW. I think if you get large positive or negative values for these it may indicate
that there is not much broadening in the Caglioti type equation, and the parameters diverge in the fit. You could play around with some dummy instrument parameters and make simulated histograms to see the difference.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">If you do not have a standard reference, you really can't deconvolute the instrument and sample effects. <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">As for the difference between old and new GSAS, I would take a look in the source code, it is well commented as to what models have been incorporated and their references. <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">Hope this helps,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Nick<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="IT" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b>From:</b> Von Dreele, Robert B. [mailto:vondreele@aps.anl.gov]
<br>
<b>Sent:</b> martedì 27 febbraio 2018 17:40<br>
<b>To:</b> Arianna Lanza <Arianna.Lanza@iit.it><br>
<b>Cc:</b> Toby, Brian H. <toby@anl.gov><br>
<b>Subject:</b> RE: instrument parameters<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Dear Arianna,</span><span style="font-size:11.0pt;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">‘Z’ is a constant Lorentzian broadening term (i.e. independent of 2-theta or TOF) recently added as it seems to be occasionally useful for some instrument characterization. As for the values, for conventional
(especially neutron) diffractometers U & W are > 0 and V < 0 so the curve is a parabola with a minimum somewhere near 2-theta for the monochromator (see the garnet neutron tutorial example in GSAS-II). Lab x-ray diffractometers will be parabolic but usually
fairly flat thus being a bit difficult to refine. Typical older ones have U~2, V~-2 and W~5. Newer ones with focusing optics will be different & smaller, however the Gaussian & Lorentzian resolution curves should be never negative. GSAS-II will show the plots
of the resolution curves for Gaussian, Lorentzian and their combination (pseudo-Voigt) as calculated and fitted – see Instrument Parameters. As Brian Toby noted, for GSAS-II the object is to calibrate your instrument with a standard (Si, LaB6, etc.) to get
good values of U, V, W (& X, Y – careful with these as sample broadening shows up in them which is NOT instrument broadening). Then never refine them again for the same instrument setup (same slits, etc.). Instead refine the sample broadening for each phase
(see the Phase/Data tab for these) as mustrain & size.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Bob<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="IT" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Toby, Brian H. [mailto:toby@anl.gov]
<br>
<b>Sent:</b> martedì 27 febbraio 2018 17:29<br>
<b>To:</b> Arianna Lanza <Arianna.Lanza@iit.it><br>
<b>Cc:</b> Von Dreele, Robert B. <vondreele@aps.anl.gov><br>
<b>Subject:</b> Re: [GSAS-II] instrument parameters<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Arianna, <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> We need to tabulate the equations we use for FWHM as a function of the profile variables somewhere (you could read the source code), but a quick answer is that you can see the resulting FWHM curves under the instrument parameters. Also,
the new parameters (Z plus a bunch of TOF terms) are generally not needed for unless one is doing unusually careful fitting of an instrument. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> First of all, I am assuming that you are fitting a standard such as NIST LaB6 that has minimal broadening. If not, you should do that before starting with a “real” sample. You don’t say but I will also assume you are using a lab instrument.
A good place to start is to fit individual peaks across the range of your pattern so you can see how the Lorentzian (gamma) and Gaussian (sigma) widths vary without constraints. You can also see how well your UVW & XY curves reproduce this. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Brian<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
</div>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">On Tue, Feb 27, 2018 at 10:00 AM, <<a href="mailto:gsas-ii-request@aps.anl.gov" target="_blank">gsas-ii-request@aps.anl.gov</a>> wrote:<o:p></o:p></p>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm">
<p class="MsoNormal">Send GSAS-II mailing list submissions to<br>
<a href="mailto:gsas-ii@mailman.aps.anl.gov">gsas-ii@mailman.aps.anl.gov</a><br>
<br>
To subscribe or unsubscribe via the World Wide Web, visit<br>
<a href="https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii" target="_blank">
https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii</a><br>
or, via email, send a message with subject or body 'help' to<br>
<a href="mailto:gsas-ii-request@mailman.aps.anl.gov">gsas-ii-request@mailman.aps.anl.gov</a><br>
<br>
You can reach the person managing the list at<br>
<a href="mailto:gsas-ii-owner@mailman.aps.anl.gov">gsas-ii-owner@mailman.aps.anl.gov</a><br>
<br>
When replying, please edit your Subject line so it is more specific<br>
than "Re: Contents of GSAS-II digest..."<br>
<br>
<br>
Today's Topics:<br>
<br>
1. instrument parameters (Arianna Lanza)<br>
<br>
<br>
----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Tue, 27 Feb 2018 16:03:36 +0000<br>
From: Arianna Lanza <<a href="mailto:Arianna.Lanza@iit.it">Arianna.Lanza@iit.it</a>><br>
To: "<a href="mailto:gsas-ii@mailman.aps.anl.gov">gsas-ii@mailman.aps.anl.gov</a>" <<a href="mailto:gsas-ii@mailman.aps.anl.gov">gsas-ii@mailman.aps.anl.gov</a>><br>
Subject: [GSAS-II] instrument parameters<br>
Message-ID: <<a href="mailto:a06a772caf334efaaa50f35772a46e32@iit.it">a06a772caf334efaaa50f35772a46e32@iit.it</a>><br>
Content-Type: text/plain; charset="iso-8859-1"<br>
<br>
Dear all,<br>
<br>
I am new to GSAS II and have no experience with old-GSAS, so forgive me for the basic level of the questions.<br>
<br>
I don't fully understand the meaning of the parameters describing the instrumental profile.<br>
<br>
? What is Z? I could not find it in the old-GSAS manual.<br>
<br>
? How can I judge if the U V W X Y Z are reasonable? (in case I don't have a reference profile from a standard) And how should a well behaved peak width plot look like?<br>
<br>
? I read that U W X Y are constrained to be >= 0, while V should be <= 0. However I have a not so badly-fitted plot where U refined to very negative, V to very positive, W is small and negative, X is positive and Y negative. So (i) those parameters
have no constraint by default!Why not? Can I do it with equations?; (ii) even from my na?ve understanding it looks like a nonsense. Most likely it is because I have broad peaks and the interplay between strain/size/etc and instrumental parameters converged
to this artificial mess. Is it possible to deconvolute the instrument contribution from the sample contribution, in absence of a standard?<br>
<br>
? SH/L is one unique parameter as opposed to 2 separate parameters in old-GSAS, what is its meaning now, the units and/or reasonable range?<br>
<br>
If you can help with even partial answers or point out useful sources of information, I will be grateful!<br>
<br>
Kind regards,<br>
<br>
<br>
Arianna<br>
<br>
<br>
<br>
<br>
,_,.-'???'-.,_,.-'???'-.,_,.-'???'-.,_,,.-'???'-.,_,.-'???'-.,_,<br>
<br>
Arianna Lanza, PhD<br>
<br>
Center for Nanotechnology Innovation@NEST<br>
Istituto Italiano di Tecnologia<br>
Piazza San Silvestro, 12, 56127, PISA, Italy<br>
<br>
<br>
-------------- next part --------------<br>
An HTML attachment was scrubbed...<br>
URL: <<a href="http://mailman.aps.anl.gov/pipermail/gsas-ii/attachments/20180227/7df88e57/attachment-0001.html" target="_blank">http://mailman.aps.anl.gov/pipermail/gsas-ii/attachments/20180227/7df88e57/attachment-0001.html</a>><br>
<br>
------------------------------<br>
<br>
_______________________________________________<br>
GSAS-II mailing list<br>
<a href="mailto:GSAS-II@mailman.aps.anl.gov">GSAS-II@mailman.aps.anl.gov</a><br>
<a href="https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii" target="_blank">https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii</a><br>
<br>
End of GSAS-II Digest, Vol 162, Issue 1<br>
***************************************<o:p></o:p></p>
</blockquote>
</div>
<p class="MsoNormal"><br>
<br clear="all">
<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<p class="MsoNormal">-- <o:p></o:p></p>
<div>
<div>
<div>
<div>
<p class="MsoNormal">Nick Weadock<o:p></o:p></p>
<div>
<p class="MsoNormal">PhD Candidate, Materials Science<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">California Institute of Technology<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">1200 E California Blvd, Pasadena, CA 91125<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">MC 138-78<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">x2520<o:p></o:p></p>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</body>
</html>