Rajesh, Physically speaking, an occupancy of one is generally defined to be a fully occupied site. So an occupancy greater than one makes no physical sense.
Perovskites *are* sometimes described as oxygen excess though, but when it says "oxygen excess" it really means "cation deficient". It is then possible that the folk doing these refinements chose to fix the cation content and let the oxygen content go high to compensate. Physically incorrect, but the maths works out as long as the overall stoichiometry is correct. Also possible, is that their data simply doesn't support the variables they are refining. jools ________________________________ From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of rajesh thattarathody [rajeshbath...@gmail.com] Sent: 09 June 2014 11:51 To: rietveld_l@ill.fr Subject: Regarding Oxygen occupancy 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
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