Dear Breogan, It could also come from the flexibility of the MOF which is really common in this class of materials (it can reach 230% in some case). Was the single crystal and PXRD measurement performed in the same condition (temperature, pressure and same solvent within the pores)? To get a better understanding, you can perform PXRD on the solid but in different conditions (ex: as-synthesized, dried, and different solvent) or even better a thermo X-ray diffraction.
Regards Hub From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Andreas Leineweber Sent: Thursday, 6 February 2014 5:25 PM To: Breogan Pato Doldan; rietveld_l@ill.fr Subject: Re: Preferred orientation and lattice parameters Dear Breogan, just three small additions: (i) .25 Å is a lot, if the lattice parameter in that direction is 4 Å, but much less if it is 40 Å.... (ii) Definitely, as Peter indicated, partial exchange of guest molecules could be responsible for the differences. This could then be indicated by a broadening of the peaks . (iii) If there is a texture as you have described, one could also consider the possibility that differently oriented crystals in your specimen have different lattice parameters. That is (effectively) the case in the case of residual macrostress, but may be also conceivable (as a slightly exotic case) in the case composition variations.... This could be checked by measuring the lattice parameters in transmission and reflection geometry. Best regards Andreas On 05.02.2014 20:11, Breogan Pato Doldan wrote: I would like to thank you both. It is a small mismatch (about 0.25 A). Due to the structure of the compound and its porosity it really makes sense that the exchange of the guest inside the cavity can affect the lattice. Regards ________________________________ De: "Peter Stephens" <peter.steph...@stonybrook.edu><mailto:peter.steph...@stonybrook.edu> Para: "Breogan Pato Doldan" <breogan.p...@udc.es><mailto:breogan.p...@udc.es>, "rietveld_l@ill.fr"<mailto:rietveld_l@ill.fr> <Rietveld_L@ill.fr><mailto:Rietveld_L@ill.fr> Enviados: Miércoles, 5 de Febrero 2014 11:55:59 Asunto: Re: Preferred orientation and lattice parameters How much mismatch? If you're getting a good profile fit, I'd be inclined to doubt that it is a consequence of preferred orientation. You could mix your sample with another material (corundum powder, cork) to try to reduce the degree of preferred orientation, and see if that makes a difference. Instead of a Le Bail fit, you could try a full Rietveld to see if the powder really is the same phase as the single crystal. One could also imagine that a powder would be more facile in exchanging solvent with the environment, which could affect lattice parameters. On Wed, Feb 5, 2014 at 1:37 PM, Breogan Pato Doldan <breogan.p...@udc.es<mailto:breogan.p...@udc.es>> wrote: Dear rietvelders, I have carried out the single crystal resolution and the PXRD Le Bail refinement of a Metal Organic Framework. The compound crystalizes as needles and there is a clear in-plane preferred orientation along the c-axis. There is a mismatch between the single crystal and the Le Bail refinement data in the lattice parameter c. Could this mismatch be due to the preferred orientations? Regards, Breogán Pato Doldán, Fundamental Chemistry Department. Faculty of Sciences. University of A Coruña Rúa da Fraga 10, 15008, A Coruña. Spain. Tel: +34 981167000 ext. 2061<tel:%2B34%20981167000%20ext.%202061> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com><mailto:alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr<mailto: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/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -- ************************** Peter W. Stephens Professor, Department of Physics and Astronomy Associate Dean for Curriculum, College of Arts and Sciences Stony Brook University (631) 632-8156 http://mini.physics.sunysb.edu/~pstephens<http://mini.physics.sunysb.edu/%7Epstephens> Please update your records to my new email: peter.steph...@stonybrook.edu<mailto:peter.steph...@stonybrook.edu> -- Dr. Andreas Leineweber Max-Planck-Institut fuer Intelligente Systeme (ehemals Max-Planck-Institut fuer Metallforschung) Heisenbergstrasse 3 70569 Stuttgart Germany Tel. +49 711 689 3365 Fax. +49 711 689 3312 e-mail: a.leinewe...@mf.mpg.de<mailto:a.leinewe...@mf.mpg.de> home page of department: http://www.is.mpg.de/de/mittemeijer
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 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/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
