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时间:2020-03-26
《Nb(110)表面氧原子覆盖度对氧分子解离的影响.pdf》由会员上传分享,免费在线阅读,更多相关内容在行业资料-天天文库。
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
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