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1、VOLUME113,NUMBER14JULY3,1991QCopyright1991bythe/AmericanChemicalSocietyAMERIWOFTHECHEMICALSOCIETYTheoreticalX-rayAbsorptionFineStructureStandardsJ.J.Rehr,*.tJ.MustredeLeon,+**S.I.Zabinsky,+andR.C.AlberslContributionfromtheDepartmentofPhysics,FM-15,Universit
2、yofWashington,Seattle,Washington98195,andTheoreticalDivision,LosAlamosNationalLaboratory,LosAlamos,NewMexico87545.ReceivedNovember13,1990Abstract:TheoreticalX-rayabsorptionfinestructure(XAFS)standardsaredevelopedforarbitrarypairsofatomsthroughouttheperiodic
3、table(ZI94).ThesestandardXAFSspectraareobtainedfromabinitiosingle-scatteringXAFScalculations,usinganautomatedcode,FEFF,whichtakesintoaccountthemostimportantfeaturesincurrenttheories:(i)anexacttreatmentofcurved-waveeffects;(ii)approximatemolecularpotentialsd
4、erivedfromrelativisticatoms,(iii)acomplex,energy-dependentself-energy;(iv)awelldefinedenergyreference.FEFFalsoyieldstablesofXAFSphasesandamplitudesaswellasmean-freepaths.Sampleresultsarepresentedandcomparedwithexperimentalresultsandwithearlierwork.Wefindtha
5、tthesetheoreticalstandardsarecompetitivewithexperimentalstandards,permittingXAFSanalysisatlowerwavenumbersandyieldingdistancedeterminationstypicallybetterthan0.02Aandcoordinationnumberstypicallybetterthan20%.Thesestandardsalsoprovidetheoreticaltestsofchemic
6、altransferabilityinXAFS.I.IntroductiontablesofMcKaleetai.)andEXCURV~takecurved-waveeffectsX-rayabsorptionfinestructure(XAFS),Le.,theoscillatoryintoaccountbutarebasedonground-statepotentialsandthusstructureintheX-rayabsorptioncoefficient,containsmuchignoreth
7、eelectronself-energy.Allofthesestandardsuseasaquantitativeinformationconcerningthelocalstructurenearanfreeparametertheenergyreferenceor"innerpotential"EO.Sinceabsorbingatom.'Thisincludesnear-neighbordistances,coor-suchadhocparameterscompensateforothererrors
8、inthetheory,dinationnumbers,andstructuralandvibrationaldisorderinbondsuchasanincorrectself-energy,theyneedhavenodirectphysicaldistances.Extractingthisinformationwithprecision,however,interpretation.Ano
