Dear Rajesh, If you mean something like LaMnO3+d, the formula should be re-written La1-dMn1-dO3 since the normal perovskite accepts no interstitial oxygen.
In other cases such as La2CuO4+d the layered strucure allows for insterstitial oxygen in the LaO layer therefore the formula is correct. Different is the possibility to do a refinement where the SOF (site occupation factor) of the oxygen atom is larger than one. In such a case, if not an error of the authors, it may well be the first mentioned case where content of La and Mn are proportionally less than one respect to O atoms but the program is reducing the scale factor to account for increased O or decreased La/Mn content. Additionally, depending on the program used for the analysis a "SOF" larger or smaller than one may have different interpretations so it may be perfectly correct to use it. Remember that, in structural refinements of all kinds the SOF have at the atom level the same efect of the scale factor (at the phase level) so the important thing is the relative values of SOF among the atoms of the phase. You can reduce all your SOFc values to 1/2 or multiply them by 2 and will obtain the same final model with a scale factor twice or half (respectively) of the initial value. I hope this rather general answer helps, it may not be useful for your specific case though, so if you have a more specific question do not hesitate in writing back, Leo 2014-06-09 6:51 GMT-03:00 rajesh thattarathody <rajeshbath...@gmail.com>: > Dear Rietvelders, > > I have seen some papers of perovskites reporting oxygen occupancy greater > than one by Rietveld refinement. Can oxygen occupancy be greater than one > ? Could you please explain its physical meaning ? > > Thanking you in advance. > > > Rajesh T > Research scholar > CSIR-National Chemical Laboratory > Pune-411008 > India > > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 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. Leopoldo Suescun Prof. Agr (Assoc. Prof.) de Física Tel: (+598) 29290705/29249859 Cryssmat-Lab./DETEMA Fax: (+598) 29241906* Facultad de Quimica, Universidad de la Republica ,_. | \ | v- ,' \ | ( \__Montevideo, Uruguay En pleno disfrute del Año Internacional de la Cristalografía 2014 ( http://www.iycr2014.org ), (http://www.cristalografia2014.fq.edu.uy)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 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/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
