Re: [Ifeffit] How to identify Mn Mn Corner edge paths in Artemis
Corner-sharing octahedra in birnessite-based structure occur either due to interlayer Mn, i.e. Mn which is attached on top of the layer, over a layer vacancy, or octahedra hanging off the edges of sheets. There is a vast litereature on this, notably from people like Manceau, Bargar and Webb. Please refer to their papers. You can get Manceau's papers by going to his website. They're all available as PDF. mam On 1/7/2014 3:51 AM, fred.mosselm...@diamond.ac.uk wrote: Hi Sathish, There are no corner sharing paths in your feff calculation as the "perfect" birnessite model you are using only has edge sharing octahedra. I am not a phyllomanganate expert so can't help with a structure suggestion to try but using google I would think you could find a structure with corner sharing MnO6. Then you could take the corner sharing path from there and the edge sharing from your original structure. In Sam Webb's paper he has refined his model to give shell occupancy numbers as he has a non totally crystalline structure. This is effectively the path degeneracy from the Feff calculation but you cannot refine this number in artemis, you have to refine Nmncor or some other variable the name is irrelevant and then define the path occupancy of the corner as 1 and the S02 for this path as amp * Nmncor . Bruce's videos are pretty good in getting started in fitting from scratch, which is really not the easiest thing to do, so keep going. I assume you have watched some of them. http://www.diamond.ac.uk/Home/Events/Past_events/XAS-workshop-2011.html?mgnlCK=1339516257183 HTH Cheers Fred ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Re: [Ifeffit] How to identify Mn Mn Corner edge paths in Artemis
Hi Sathish, There are no corner sharing paths in your feff calculation as the "perfect" birnessite model you are using only has edge sharing octahedra. I am not a phyllomanganate expert so can't help with a structure suggestion to try but using google I would think you could find a structure with corner sharing MnO6. Then you could take the corner sharing path from there and the edge sharing from your original structure. In Sam Webb's paper he has refined his model to give shell occupancy numbers as he has a non totally crystalline structure. This is effectively the path degeneracy from the Feff calculation but you cannot refine this number in artemis, you have to refine Nmncor or some other variable the name is irrelevant and then define the path occupancy of the corner as 1 and the S02 for this path as amp * Nmncor . Bruce's videos are pretty good in getting started in fitting from scratch, which is really not the easiest thing to do, so keep going. I assume you have watched some of them. http://www.diamond.ac.uk/Home/Events/Past_events/XAS-workshop-2011.html?mgnlCK=1339516257183 HTH Cheers Fred -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
[Ifeffit] How to identify Mn Mn Corner edge paths in Artemis
Dear all I am sorry for disturbing you all again, since I am self learning to fit multiple scattering for biogenic Mn oxides in Artemis, I am quite lost in understanding the basics of Mn Mn corner sharing path. All reports are included Mn-Mn Corner at ~ 3.4 A, which I cannot find in my Feff calcuation for Phyllomanganate layer (Na-Birnessite) model. Below are the crystallographic information of Na birnessite I used (*also available in the attachment*), Na is excluded. A = 5.174 B = 2.850 C = 7.336 and angles 90, 103.18 and 90 for alpha, beta, gamma respectively Parameters X YZ Mn 0 00 O10.37600 00.1330 I have two questions 1) How to identify the Mn Mn corner paths from the Paths result. 2) Where can I find the Coordination Number for Mn Mn Corner, If i see in eg. Webb et al., 2005 ( http://www.intl-ammin.geoscienceworld.org/content/90/8-9/1342.short) the CN numbers for Mn-Mn Corner is 0.6(1.0) or 0.8(8), what does the number represent in the brackets? It will be looking forward for your help. Regards -- Sathish Na_Birnessite.inp Description: Binary data Na_Birnessite_Paths_Feff cal.yaml Description: Binary data ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
