氧化锌晶体生长基元模拟_英文_

1、第36卷第5期人工晶体学报Vol.36No.52007年10月JOURNALOFSYNTHETICCRYSTALSOctober,2007GrowthUnitSimulationofZnOCrystalZENGLing2ke,LIPing,LIXiu2yan,SHUIAn2ze,LIUPing2an,WANGHui,CHENGXiao2su(1.DepartmentofMaterialScienceandEngineering,SouthChinaUniversityofTechnology,Guangzhou510640,China;2.CollegeofChemistryandChemic

2、alEngineering,SunYATUniversity,Guangzhou510640,China)(Received8May2007)22Abstract:GrowthunitZn(OH)4forZnOcrystalwassystematicallysimulatedwiththeHyperchem1121111moleculesimulationsoftware(HypercubeInc.).Thegrowthunitconnectionrulewasdiscussedthroughanalyzingconnectingwaysofthegrowthunits.Thesimulati

3、onresultsshowthatlexcompoundwillbecomestablerwhentheratioofZnatomnumbertothehydroxylnumberislessinthesameratiocondition.Furthersinglecrystalwithnanorodornanowireisdifficulttopsimulatingthelinearconnectionofthegrowthunits.KeycrystalCLCnumber:Documentcode:AArticleID:10002985X(2007)0521166207氧化锌晶体生长基元模

4、拟曾令可,李萍,李秀艳,税安泽,刘平安,王慧,程小苏1121111(1华南理工大学材料学院,广州510640;2中山大学化学与化学工程学院,广州510640)摘要:本文利用Hyperchem分子模拟软件对氧化锌晶体生长基元Zn(OH)422进行了系统的模拟。通过模拟分析生长基元的结合方式,提出了生长基元的结合规律。结果表明:Zn原子数(生长基元)与共用O原子数(O桥)的比例越大所形成的络合物越稳定;当分子中Zn原子和共用O原子比例一定时,羟基数目越少则越稳定。并且通过计算机模拟生长基元直线状结合情况解释了单晶ZnO纳米线状或纳米棒状的结构很难在实验中获得的原因。关键词:生长基元;模拟;氧化锌晶

5、体1IntroductionZincoxide(ZnO)isamulti2functionalmaterial,whichhasbeenusedingassensors,pressuresensitive,catalystandopto2electricdevicesfields.Researchesaboutthezincoxidehavebeenrapidlyexpanding.InordertostudythestructureofZnOcrystalanditsformationprocesses,thegrowthunitmodelofanioncoordinationpolyhed

6、ronwasintroducedinthispaper.Thegrowthunitmodelofanioncoordinationpolyhedronemphasizestheinfluenceofintrinsicstructureofcrystalandtheimportanceoftheexternalconditionsonthecrystalgrowth.Itisusedtoanalyzesomeproblemsincrystalgrowththeory,suchasformationofdendriteincrystalstructure,theReceiveddate:20072

7、05208Foundationitem:TheprojectsupportedbytheResearchFundofScienceandTechnologyCommissionofGuangzhouMunicipality(No.2002Z32D0121)1Biography:ZENGLing2ke(19442),Male,fromGuangdongprovince,Professor.E2mail:imjqlab第5期ZENGLing2keetal:GrowthUnitSimulationofZnOCrystal1167growthhabitofpolarcrystal,andformati

8、onofallomerismandpolymorphism.Fromthemicroperspective,crystalgrowthprocessisaunitprocess.Thisprocessincludesthefollowingmainsteps.Thefirststepistheformationofaunit.Thentheunitisabsorbedbygrowthinterphaseandmovesoninterphasefreely.Finally,theunitwillbecomepartofthecrystalorgoawayfrominterphase.Intern

9、alcrystalstructure,environmentalconditionsandgrowingconditionsareimportantfactorsincrystalgrowthunitprocess.Crystalwithdifferentstructurehasdifferentgrowthexternalitiesanddifferentgrowingconditionwillleadtodifferentcrystalstructure.ZhongWei2zhuofirstlyputforwardthegrowthunitmodel,whichthegrowthunito

10、fZnOcrystalwasZn(OH)4226.UsingthemethodsofmolecularsimulationandHyperChemv.7.0programs(PM3method),wesimulatedthegrowthunitsystematicallyinthisstudy.HyperChemisoneofarapidlygrowingnumberofmolecular2modelingprogramsforthepersonalcomputer(PC).Thispackageallowsonetodraw,edit,andmanipulate5moleculestocal

11、culateenergiesandtooptimizemoleculargeometriesusingeithermechanicsorsemiempiricalquantummethods,andtoperformmoleculardynamicssimulations.mechanicsincludesfourforce2fieldmethods:MM1,AMBER,OPLS,andBIO1.mieincludeextended2Huckel,CNDO,INDO,MINDO3,MNDO,MNDO/3,DO/2.72FormationprocessofWiththeollreactionpo

12、ssiblyoccursinthesolution.+OHZnOH+2ZnOH+OHZn(OH)2Zn2+(1)(2)223242Zn(OH)2+OHZn(OH)3Zn(OH)3+OHZn(OH)4Zn(OH)4Zn(OH)52232(3)(4)(5)(6)22+OHZn(OH)5+OHZn(OH)6ThebindingenergiesofthepossiblecomplexcompoundsarelistedinTable1.Whenthebindingenergyislargeinthenegative,itisdifficulttobreakthecomplexcompound,andt

13、hecomplexcompoundisstable.Table1Bindingenergy(kcalmol)ofsomecomplexcompoundsinformationprocessofthegrowthunitZn(OH)4MolecularformulaZnOH+Zn(OH)2Bindingenergy53.243MolecularformulaZn(OH)3Zn(OH)222221Bindingenergy2288.3412510.135MolecularformulaZn(OH)532()42Bindingenergy2508.065BondlengthofZn2OHisthep

14、rogramdefault(1.98)AsshowninTable1,withtheincreaseofOH,thebindingenergyofthecomplexcompoundswillbelarge+22negativelyfromZnOHtoZn(OH)4.ThisindicatesthatthecomplexcompoundmoleculebecomestableandisaspontaneousprocessfromZnOH+22toZn(OH)4.Butthebindingenergyofthecomplexcompoundsgradually22reducedintheneg

15、ativefromZn(OH)4toZn(OH)6.TheseresultsshowthattheZn(OH)4+4222isthestablestinisverydifficulttotheprocess.Inaddition,thebindingenergyofZnOHispositive,anditindicatesthatZnOH+existinthesolution.Theseresultsareconsistentwithliteraturereports.3TheeffectofpHongrowthunitWhenpHvaluechanges,concentrationofHor

16、OHwillbealtered,thentheattractionorrepulsionofhydroxylwillchange.ThusthebondlengthofZn2OHwillbestretchedorshortened.ThesimulationresultsarelistedinTable2.+116821人工晶体学报22第36卷Table2Bindingenergy(kcalmol)ofthecomplexcompoundZn(OH)4withdifferentbondlengthstructureBondlength1.98istheprogramdefault.22Asse

17、enfromthetable,whetherthebondlengthstretchesorshortens,thebindingenergyofZn(OH)4willreduceinthenegative.Clearly,thepHwillinfluencethestabilityofthegrowthunit,whichshouldexiststeadilyinacertainrangeofpHvalue.4Theconnectingwaysbetweengrowthunits22GrowthunitZn(OH)4,withtetrahedroninsolution.Whentheunit

18、isconnectedbysharingcorner,thecomplexcompoundswillbedifferent.TheresultsarelistedinTable3Binmolofthecomplexcompoundsconnectedbysharingcorner,edgeorface2AsshowninTable3,thebindingenergyofthecomplexcompoundsconnectedbythesharingcornerislargerinthenegativethanthatconnectedbythesharingedgeorface.Thecomp

19、lexcompoundconnectedbythesharingcorneristhestablestinthesystem.Thebindingenergyofthecomplexcompoundsconnectedbythesharingfaceismuchlessinthenegativethantheothertwoways.Andthecomplexcompoundconnectedbythesharingfaceisextremelyunstable.Theseresultsalsoareconsistentwithcrystalfieldtheory.5Growthunitsco

20、nnectedbylinearconditionWhenthegrowthunitsareconnectedtogetherbylinearconditions,howwillthebindingenergychange?AsshowninTable4andTable1,whenthereisonlyonegrowthunit,thebindingenergyisabout2588kcalmol.Whiletherearetwogrowthunits,thebindingenergyisabout2623kcalmol,thelargestinthenegative.Withincreasin

21、gthegrowthunit,thebindingenergyofthecomplexcompoundsreducesinthenegative.Theseresults42showthattwogrowthunitseasilyintegrateintoacomplexcompoundZn2O(OH)6insolution,whichisaspontaneousprocess,butitisdifficulttoconnectmoregrowthunitsbylinearcondition.Therefore,theZnOsinglecrystalnanorodornanowirewasdi

22、fficulttoobtaininpractice.2121第5期ZENGLing2keetal:GrowthUnitSimulationofZnOCrystalTable4Bindingenergy(kcalmol)ofgrowthunitsconnectedbylinearcondition2111696GrowthunitsconnectedindifferentjointwaysTable5listsallthejointwayswhentherearetwo,threeandfourgrowthunitsrespectively.Table5Bindingenergy(kcalmol

23、)whengrowthunitconnectedindifferentjointWays211170人工晶体学报第36卷续表第5期ZENGLing2keetal:GrowthUnitSimulationofZnOCrystal1171续表5StatisticsofTable5arelistedinTable6.AsshowninTable5orTable6,thecomplexcompoundofZnatomnumbertoObridgenumberislarger,anditwillbecomelessinthesameratiovaluecondition.Thisrulecanrevea

24、lthegrrthegrowthofZnOcrystal,thenumberof2OHwillgraduallyreduceoutsidetheboundaries.Assumingthatthemolecular(z+2y22x)22formulaofcompy()z,whenzisenoughlittleandxandyareenoughlarge,OHcanbeneglectedxyThusZnOwillbeobtained.Table6StatisticsofgrowthunitconnectedindifferentjointwaysNumberofZnatom432434Numbe

25、rofObridge111223Numberofhydroxyl12961189RangeofbindingenergyminmaxNumberofZnatom43444NumberofObridge33445Numberofhydroxyl106786261715.510Rangeofbindingenergyminmax(2y222willbeobtained.InordertokeepZnxOy(2y22x)2neutral,xshouldbeequaltoy.2988.5932869262426172457228228682620251323752215213328643.813284

26、2814107ConclusionsTheconclusionsaresummarizedasfollows.(1)Zn(OH)422isthestablestinthegrowthprocessofthegrowthunit;(2)pHwillinfluencethestabilityofthegrowthunit,whichshouldexiststeadilyinacertainrangeofpH;(3)Thecomplexcompoundsconnectedbysharingcorneristhestablest,andthatconnectedbysharingfaceisextre

27、melyunstable;(4)TwogrowthunitseasilyintegrateintoacomplexcompoundZn2O(OH)642,whichisaspontaneousprocess,butitisdifficulttoconnectmoregrowthunitsbylinearcondition.ThisisthereasonwhytheZnOsinglecrystalnanorodornanowirewasdifficulttoobtaininpractice;(5)ThecomplexcompoundwillbecomestablerwhentheratioofZ

28、natomnumbertoObridgenumberislarger,anditwillbecomestablerwhenthehydroxylnumberislessinthesameratiocondition.ThisrulecanrevealthegrowthprocessofZnOcrystal.1172人工晶体学报第36卷References1LiXY.StudyonPreparationofZnOUltrafinePowdersbyPrecipitationTransformationMethodD.SouthChinaUniversityofTechnologyDisserta

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