Negative Biso / absorption in TOPAS.

Dear colleagues, I am helping some people from the University of Frankfurt with their Rietveld refinements, and usually their powder patterns are measured on their own instrument and the refinements are excellent. This time, however, they have to work with a powder pattern that was sent to them.

Re: Negative Biso / absorption in TOPAS.

Jacco, could you kindly tell us the composition of the sample and the technique used to collect the data ? Lubo On Wed, 10 Feb 2010, Jacco van de Streek wrote: Dear colleagues, I am helping some people from the University of Frankfurt with their Rietveld refinements, and usually their

Re: Negative Biso / absorption in TOPAS.

Lubomir Smrcok wrote: could you kindly tell us the composition of the sample and the technique used to collect the data ? The technique to collect the data is unfortunately not known to me, I'd have to ask. The composition is not a secret: it is an organic pigment, Pigment Yellow 110, and its

Preferred orientation question

Dear All, Could anybody help me with a question I have related to preferred orientation? I have collected some spectra of a sample, on a D4 using flat plate geometry, that I suspect is showing preferred orientation effects. I was under the impression that a way of testing for this is to re-pack

Re: Negative Biso / absorption in TOPAS.

1. Is absorption indeed the most likely cause of this problem or are there other possibilities? 2. How do we model absorption in TOPAS? Which keyword do we use and what are reasonable values for the parameters in the expression? 1. You will find discussions of negative B-factors in the

Find-it

Hallo, I have problem to use FINDIT software: after the starting windows, sometimes it freeze. Is there anyone that know how resolve this problem? Thank you Davide Prof. Davide Levy DSMP Università degli Studi di Torino tel. +390116705122 fax +390112365122 skype davidelevy

The 5th Reynolds Cup

Dear people interested in the Rietveld method, you may be interested in the Reynolds Cup 2010 will see the staging of the 5th Reynolds Cup competition in quantitative mineralogy. The biennial Reynolds Cup was started in 2000 by Dougal McCarty, Jan Środoń, and Dennis Eberl in honour of Bob

Re: Find-it

I have problem to use FINDIT software: after the starting windows, sometimes it freeze. Is there anyone that know how resolve this problem? FINDIT runs the PC version of the ICSD database. My personal opinion :-) is that you should switch to the WWW version on http://icsd.fiz-karlsruhe.de/ You

Re: Find-it

Dear Alan, isn't it a little bit unfair to list just the Pros but skip the Cons? We used to have a FINDIT subscription several years ago. Sadly, our purchasing department canceled the subscription when we got institutional access to the WWW version. If I remember correctly, FINDIT had far more

Re: Preferred orientation question

Dear Ross, I presume on the flat sample you measured regular theta-2theta diagrams, then only probed those planes parallel to the sample plane. In such a situation, you do not probe correctly the texture, and all the models you could envisage are just giving back parameters that have been

Re: Find-it

Dear Frank, As I wrote, I was referring to my personal opinion and the new ICSD WWW pages on http://icsd.fiz-karlsruhe.de/ which do allow consecutive searches, combination of results and methods of searching for similar structures, structure-types etc. FIZ provides both WWW and FINDIT versions

Re: Find-it

Dear Alan, so it seems I am using an Interface version which is too old. I guess I should urge the responsibles to update it. Thanks for the information. Best wishes, Frank Alan Hewat wrote: Dear Frank, As I wrote, I was referring to my personal opinion and the new ICSD WWW pages on

RE: Negative Biso / absorption in TOPAS.

Is it possible the data was collected with variable slit aperture? You could try to convert the data to fixed slit aperture intensities and see what happens to the B values. Regards, Jeff Nicolich W.R. Grace Co. - Conn. 62 Whittemore Ave, Cambridge, MA 02140 +1-617-498-3816