Rietveld原理.ppt

《Rietveld原理.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、陈小龙中国科学院物理研究所2006.10杭州LecturenotesRietveld方法原理IsostructuralCompoundsNd2CuO4Gd2CuO4a=0.39419nma=3.8938nmc=1.21627nmc=11.8810nmZNd=0.353ZGd=0.349Nd(Gd)XRDpatternsofSolidsolutionNaSr4-xBaxB3O9(0≤x≤4):FirstcubicborateonlywithBO3Cubicboratesareestimatedbel

2、ow1%.L.Wu,X.L.Chen,et.al.2004PhasetransitionofBaTiO3fromtetragonaltocubicatabout132˚CYBa3B3O9:PhasetransitionandstructuredeterminationS.G.:P63cm(No.185)a=9.4235(4)Å,c=17.602(1)Å1100CS.G.:R-3(No.148)a=13.0441(1)Å,c=9.5291(1)Å1140CX.Z.Li,X.L.Chen,et.a

3、l.2004LiAlB2O5:SearchfornewSHGmaterials[B3O7]5-&[AlB2O7]5-StructuralDataforLiAlB2O5FinalRefinementofNewcompoundofLiAlB2O5StructurevsTemperature:KCaCO3F0.8120(3)0.1880(3)0.5byx-raydataLiSr4B3O9:Acomparisonbetweenstructuredeterminationfromsingle-crystal

4、andpowderX-raydiffractiona=14.9470ÅS.G:Ia-3d(ZB/ZSr)2=(3/38)20.6%Single-crystal:Rint=0.0745R1(alldata)=0.0695wR2(alldata)=0.1887withweightingscheme:W=1/[σ2(Fo2)+(0.0000P)2+359.71P]whereP=(Fo2+2Fc2)/3SDPD:RB=0.07Rp=0.0609Rwp=0.0811Rexp=0.0314WhatisaRi

5、etveldRefinement?-astandardtreatmentofpowderdiffractiondatatomakethefinalstructuralmodelachievetheacceptedcriterion;-abestknownmethodthatfullymakesuseofthestep-modescanneddatatodigoutalotofstructuralandotherinformation;-aprocedureforstructuralsolution

6、innature.WhatcanwegettoperformaRietveldrefinement?LatticeParametersQuantitativephaseAnalysisAtomicPositionsGrainsizeAtomicOccupancyIncommensurateStructureDebyeTemperaturesStructurefactorsCrystallinityPhasetransitionsMagneticstructures……HistoryReviewRi

7、etveldoriginallyintroducedtheProfileRefinementmethod(Usingstep-scanneddataratherthanintegratedPowderpeakintensity)(1966,1967)RietvelddevelopedfirstcomputerProgramfortheanalysisofneutrondataforFixed-wavelengthdiffractometers(1969)Malmos&Thomasfirstappl

8、iedtheRietveldrefinementmethod(RR)foranalysisofx-raypowderdatacollectedonaGinierHaggfocusingCamera(1977)Khattack&CoxfirstappliedtheRRtox-raypowderdatacollectedonadiffractometer(1977)ConferenceonDiffractionProfileAnlysisSponsoredbyIUCrinPoland,