第38卷第1期燃料化学学报V01.38No.I2010年2月JournalofFuelChemistryandTechnologyFeb.2010
文章编号:0253-2409(2010)01-0121-08
SurfacestructuresofFe304(111),(110),and(001)
Adensityfunctionaltheorystudy
YANGTao,WENXiao-dong,RENJun,(StateKeyLaboratoryofCoalConversion,InstituteofCoalLIYong—wang,WANGJian-guo,HUOChun-fang
Chemistry,ChineseAcademyofSciences,Taiyuan030001,China)
Abstract:ThesurfacestructuresofFe304(111),(1lo)and(001)havebeenstudiedatthelevelofdensityfunctionaltheory.Iti8foundthattherearetwomoststableFe304(1l1)surfacesincloseenergyandterminatedwiththeexposedtetrahedralandoctahedralironlayers.,BothFe304(110)andFe304(001)surfaceshavetwo¥ui-faceterminationsinCloseenergy.11Iecomputedresultsagreewellwiththeexperiments,andexplainreasonablytheobserveddiversityand
complexityofthe
experiments.necomputedsurfacefreeene:rgiesindicatethat(1l1)islessfavourablethermodynamicallythan(110)and(001),andtheformationof(1l1)shouldbekineticcontrolled.
Keywords:Fel04;structure;stability;DFr
CLCnumber:0643Documentcode:A
“Magnetitet(Fe304)isconsidereda8olleofthe
mostimportanttransitionmetaloxidesandwidelyused
fordifferenttechnologicalapplications.such船
magneticstorageofinformation[1|,corrosioncontrol[2】
andheterogeneouscatalysis【31.Thepredominant
naturalgrowthfacesofFe304are(111)and(001)
while(110)islessknown‘4。.Althoughmany
experimentalstudieshavefocusedonthestructural
analysisofFe304byusinglowenergyelectron
diffraction(LEED)"-8],scanningtunneling
microscopy(STM)"叫41,andX—rayphotoelectron
diffraction(XPD)㈦16],itisstillco玎troversialabout
the
precisestructures
ofmagnetitesurfacesuptodate.
ForFe304(111),therearesixterminationsby
cuttingthespinel(111)stackingsequence.They
exposetetrahedral(FeteIlorFetet2)andoctahedral
(FeoctlorFeoct2)coordinatedFeatoms,aswellas
closelypackedOlayers(01or02).Lennieetal【to]
investigatedFe304(111)byusingSTM,andfound
thattherearetwoterminations(AandB):termination
AhasanunreconstructedFe304(111)with3/4MLof
Featomsand1/4MLofOatoms
exposedovera
closelypacked
Olayer,andterminationBhasanunreconstructedFe304(111)with1/2MLofFeatomsexposedoveracloselypackedOlayer.Theyproposed
thatterminationBshouldbeterminationA.Lemireeta1.[17】
morestablethansuggestedthatFe304
(111)isterminatedby1/2MLofFe,withanoutermost1/4ML
consistingofoctahedralFe2+situatedabovean1/4MLoftetrahedralFe3+byusingCOadsorptionmethod.OnthebasisofSTM.Weissetalm驯suggestedthatFe304(111)isterminatedby1/4MLofFeandtheoutermostiion
planeisrelaxed
inwardtowardstheunderlying
oxygenplane.TheyalsosuggestedthattheunstableFe304(儿1)CallbestabilizedbyremovingFeatomsfromthetopmostsurfacelayertherebycreatingvacancies.OnthebasisofSTM.Condonetal[9]
terminatedwith1/4ML
proposedthatFe304(111)is
Featoms.However,Kimetal¨“suggestedthatFe304(111)maybeterminatedbyoxygenbyusingLEED,STMandXPD.Berdunoveta1.¨“foundtheoxygenterminatedFe304(111)wasverystableatroomtemperature.RecentabinitioperiodicHartree—Fockcalculation【22】confirmedthatFe304(111)consistingoftwooutermostFelayersismoststable.Furthermore.excesssurfacechargesL玛ohavebeenusedtopredictthestableterminated(111)surface,andthelayerwith1/4MLoftetrahedralFe
atomwiththeleastexcesssurface
chargeismost
stable.Applyingthe
concepts
offirst—principlethermodynamics.Zhueta1.analyzedthestructureofFe304(111)attheequilibriumwithanoxygenenvironment[24].TheircalculationsrevealedthattheFe。。t2——Fetetl——01—_te瑚inatedsurfaceisenergeticallyfavoredandtheFeoc“一02一te彻inatedsurfaceismoreactivethantheothertwoFe.terminatedsurfaces.ApartfromFe304(111),Fe304(110)hasalsobeenstudied.Therearetwosuccessivealternatinglayers,e.g.;A?layerwithbothoetahedralandtetrahedralcoordinatedFeatoms,whileB—layerwith
Receiveddate:2009-04一ll;Receivedinrevisedform:2009-07一l8。
Foundationitem:National
NaturalScienceFoundationofChina(2047311l,20590361);NationalOutstandingYoungScientistsFoundationofChina(20625620)。
Correspondingauthor:HUOChun—fang。E—mail:heD05@sxicc.ac.ca。
Authormtroducfion:YANGTao(1980一),female,Doctorstudent,engagedinDFFstudyonFe304surfacepropertiesandre.actionmechanism。
本文的英文电子版由Elsevier出版社在ScieneeDirect上出版(http://www.scieneedireet.com/scieneB/joumal/18725813)。
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