Nb(110)表面氧原子覆盖度对氧分子解离的影响.pdf

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1、物理化学学~E(WuliHuaxueXuebao)FebruaryActaP．一Chim．，z．2013，29(2)，365-370365[Article]doi：l0．3866／PKU．WHXB20121l144www．whxb．pku．edu．cnNb(110)表面氧原子覆盖度对氧分子解离的影响王清高尚家香(北京航空航天大学材料科学与工程学院，北京100191)摘要：用基于密度泛函理论的第一性原理方法研究了Nb(110)表面氧原子覆盖度分别为0．25、0．5O、0．75和1．00单层时对氧分子解离的影响．结果表明，在氧原子覆盖度不

2、大于O．50单层时，由于氧分子和表面铌原子的较强相互作用，使它们能够自发解离．然而在氧原子覆盖度为0．75单层时，氧分子只能够在未占据的洞位附近解离，同时发生严重的晶格畸变．在形成一个氧原子单层后(1．00单层)，氧分子只能弱吸附在Nb(100)表面上，此时氧原子向内扩散成为氧分子继续解离的速率决定步骤．这些结果从理论上解释了在形成一个氧原子单层后，Nb(110)表面氧分子吸收速率迅速下降的原因．关键词：密度泛函理论：氧原子：氧分子：Nb(110)表面中图分类号：0647EfectsofOAtomCoverageontheDissoc

3、iationof02MoleculesontheNb(110)SurfaceWANGQing—GaoSHANGJia-Xiang(SchoolofMaterialsScienceandEngineering,BeihangUniversity,Beij'ing100191，PR．China)Abstract：TheeffectsofoxygenatomcoverageonthedissociationofO2moleculesattheNb(11O)surfacewereinvestigatedusingdensityfunction

4、aItheoryfDFT)methods．ThedissociationofO2moleculesisfacileatlowOcoverages[0≤O．50monolayer(ML)1becauseofthestrongelectronicinteractionbetweenO2moleculesandtheNbsubstrate．Atacoverageof0．75ML．O2moleculesnexttounoccupieddistortedfour—f0ld(H4d)sitesonlydissociatewithseverelat

5、ticedistortions．However,theinwarddiflusionofOatomsistheratelimitingstepforthedissociationofO2moleculesafteradsorptionof1．00MLOatoms．Overall，ourtheoreticaIstudyprovidesarationalefortheexperimentaJresultthatthedissociationofO2moleculesdecreasesmarkedlyafterrapidadsorption

6、of1．00MLOatomsontheIowjndexNbsurfaces．KeyWords：Densityfunctionaltheo~；Oatom；O2molecule；Nb(1101surface1lntroductiondividedintothedissociationofO2molecules．followedbytheNiobiumhasbeenusedforfabricatingsuperconductingra-latticepenetr~ionofOatoms，andfinallythegrowthofoxided

7、io~equencycavitiesandtunnelbarriers，～however,theirper—phases．Forthisreason．thedissociationofO2moleculeshasformancesmaybedestroyedbytheNboxidization．Manyex—beeninvestigatedexperimentally．FarrellandPanteleta1．ob—perimentsweredonetoclarifytheoxidationoflowindexNbtainedthes

8、tickingcl／rvesof02onthe1owindexNbsurfaces，surfacesusingAugerelectronspectroscopy,X—rayphotoelec—respectively~T