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1、材料科學(xué)基礎(chǔ)材料科學(xué)基礎(chǔ)FundamentalofMaterialsFundamentalofMaterialsFundamentalofMaterialsFundamentalofMaterialsProf:TianMinBoTel:62795426，62772851E-mail:tmb@mail.tsinghua.edu.cnDepartmentofMaterialScienceandEngineeringTsinghuaUniversity.Beijing100084Lessonnine§§3.4
2、SomeRulesGoverningthe3.4SomeRulesGoverningtheIonicCompoundsIonicCompoundsPauling’sthreerulesgoverningthestructureofioniccompounds.1.AnionCoordinationpolyhedronruleEachcationissurroundedbyananionpolyhedron,thedistancebetweenanionandcationisro＝r+＋r-,whilet
3、heCNdependsonr+/r-.unstableunstablero＞r+＋r－ro＝r+＋r－stableioniccompoundstablestablero＜r+＋r－thereissomecovalentbounding+anionrCN＋()min?polyhedronrhexahedron80.732octahedron60.414tetrahedron40.225trigonal30.1552.ValenceruleThereisadefiniterelationbetweenval
4、enceandCN.LetSbethestrengthofelectrostaticbondingbetweenapairofanionandcation+ZS=+CNwhere,S:bondingstrength+Z:numberofvalenceelectron+CN:C.N.ofcationion+?CNCN+?Z=∑Si,Z=∑Sii=1i=1ifS1＝S2＝……＝S,ThenZ＝(CN－)×S＝（CN－）×（Z+/CN+）3.Theanionpolyhedronprefertoshareape
5、xinsteadofsharingedgesorfaces:§§3.5CrystalStructureofCeramic3.5CrystalStructureofCeramicMaterialsMaterialsABAB2A2B3ABO3AB2O4?ⅠⅠ.ABtype.ABtype1.NaClr+/r－＝0.54∴octahedron＝>CN+＝6Z－＝1＝CN－(Z+/CN+)＝CN－×1/6∴CN－＝62.CsClr+/r－＝0.91∴hexahedron＝>CN+＝8Z－＝1＝CN－(Z+/CN+
6、)＝CN－×1/8∴CN－＝83.Zincblende(ZnS)CN－＝4CN+＝44.Wurtzite(ZnS,ZnO)18S(O)＝1/2＋1/2＋11＝22Zn＝1/4×4＋13＝28?120:S(O):Zn?ⅡⅡ.AB.AB22typetype1.Fluorspar(CaF2)Li2ONa2O+r=0.75?rCN+＝8CN-＝42.Rutile(TiO2)+r=0.48?r+CN=642∴S==63?2?2=CN()?CN=33?ⅢⅢ.A.A22BB33type()type()α?Al2O3+
7、31CN=6S==62?12=CN()2?∴CN=4?ⅣⅣ.ABO.ABO33type(BaTiOtype(BaTiO33,CaTiO,CaTiO33))2r+r=aAO21r+r=aBO2∴r+r=2(r+r)AOBO?ⅤⅤ.AB.AB22OO44type(spinel,MgAltype(spinel,MgAl22OO44)Mg:4＋4＝8Al:4×4＝168(MgAl2O4)O:4×8＝32ExamplesandDiscussionsExamplesandDiscussionsExerciseExe
8、rcise（更多考研考博資料（更多考研考博資料博宸客博宸客服服扣扣：扣扣：924527819924527819924527819924527819924527819924527819924527819924527819））Thankyou!Thankyou!99
