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Fe_3O_4(111),(110)和(001)表面结构的密度泛函理论研究

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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