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2σu(强反键 σ

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1σg(强成 PropertiesofEnergyEnergylevelsarefunctionsofR,inter-atomicdistancewithdistanceSymmetryofatomicwithdistanceOrbitalSymmetry1.Theprincipleofthelowest1.TheprincipleofthelowestTheenergylevelsarecorrelatedinorderTheenergylevelsarecorrelatedinorderofincreasing2.TheNon-Crossing2.TheNon-CrossingTwocorrelatinglinescharacterizedthesameTwocorrelatinglinescharacterizedthesamequantumnumberandparityshouldnevercrosseach轨道能~键

变化过程与守 对称性对称性

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u uu u

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双原子分DiagramofSymmetry结论:问题(2sB(2sA(1sB(1sA离产物吗R=pCommentspCommentsontheDiagramofSymmetry(2sB(2sBLi++ (1s)2 (1)2=R=Li(1sLi)2CommentsontheDiagramofSymmetryDiscussionofLiHdissociationAccordingtothediagram (1)2(2Li++ (1sLi++ (1s)2Li(1sLi)2(2sLi)1+ R0R Full

为什么ValenceValenceBondTheory(VB)forValenceBondTheoryinGeneralManyElectronTheories:MOandMolecularMolecularOrbitalTheory(MO)forMOMOv.s.MolecularOrbitalTheory(MO)forValenceBondTheory(VB)forValenceBondTheoryinGeneralMOv.s.MOv.s.CoulsonChapterCoulsonChapterMolecularOrbitalTheory(MO)for1

利用B.O.近似,H2分子中电子运动的Schrödinger方程HH ˆ122 21211111r12MolecularOrbitalTheory(MO)forOrbitalB2r(2)B2r(2)E(2)rB11122221ˆH(2) rr1112121ˆH(1) 2EachofwhichissimilartotheequationforH

RisneglectedforitisMolecularOrbitalTheory(MO)forOrbital ()2AB 2(AB+12 AB12 AB电子自旋MolecularOrbitalTheory(MO)forOrbitalGroundandexcitedstatesofGroundGroundExcitedMolecularOrbitalTheory(MO)forOrbitalGroundGroundstateofH2 g1

1(1)(2) 2 MolecularOrbitalTheory(MO)forOrbitalGroundstateofGroundstateofH2,gBond1.57a0(841.40a0(742.65eV(2564.75eV(458Bond1.57a0(841.40a0(74Bond1.57a0(841.40a0(742.65eV(2564.75eV(458Errorscomefrom pletebasissetinMolecularOrbitalTheory(MO)forOrbitalExcitedstatesofH2,

称 称TT

1

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S(1,21(1)(2(2)(1)1(1)(2(2) S 2 B1s(1)A1s1A1A2AB2B1B1BA B1s(1)B1sAyzetheLCAOWavefunctionsofGroundstate为什么MO方法无法给出正确的解理极H1A2B2A1BH1A2B2A1B1 1

22Wrongdissociation1:1

(2) (2) (2) ValenceBondTheory(VB)for 1

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Strongere-eHigherCouldbeneglectedinsome 两个孤立的氢氢分

追循量子化学发展的历程Heitler-London(HL)vs.MOwaveForH-H,χa,χbareatomicorbitals thenormalization

(2)

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H-H+,H+H-ValenceBondTheory(VB)for 1A2B2A1BCombinationoftwoneutralTheonlythingleftistocalculatetheenergyoftheTheyarethevalencebondwavefunctions roundandexcitedstateresectivelH2分子的全数:完全波数是述空波函乘.,自旋波函数包括三个对函数和一个 称函数: 称自旋波函数相乘,后者(略去归一化系数)代表明两个H接近时,若电子自旋反平行,可形成电电子配对法对键.为电子配对提供了理论说明.对电子配对法ValenceValenceBondTheory(VB)forSS1sA(1)1sB(2)1sA(2)1sB(1)1(1)(2)2(1S22 1,21s(1)1s(2)1s(2)1sABAB12122(1S2TValenceBondTheory(VB)forState *ˆdH1SB(2)ˆsAH121sAB(2)ˆsA(2)1sBValenceBondTheory(VB)forStateˆˆ1212221r1rrrB2r12121211r211rB122rrB2r1RH121rRValenceBondTheory(VB)for(2)ˆsA 1 2HAB1211rRA1 2B1s(1)1s(2)1s(1)1sSimilartoJinthecaseSimilartoJinthecasemany-electronmany-electronmany-electronSimilartoJinthecase

ValenceBondTheory(VB)for1s(1)1s(2)AB12211r11s(1)1s(2)AB12211r11s(1)1sArB1B 1s(1)1s 121AB21rA11s(1)1sAB 1s(1)1s(2)AB1 B1r1s(1)1sAB1s(1)1s(2)E1s(1)1sABAB 1s(1)1A B1r1sA 1s(2)1s1BB2E1sH JRValenceBondTheory(VB)for

1sA(1)1sB(2)ˆsA(2)1sB 1 2

11 2rR rR

121sA(1)1sB(2)H11sA(2)1sB 1s(1)1s(2)1s(2)1s

1

1 1

SimilarSimilartoKinthecasemany-electronSimilarSimilartoKinthecaseofmany-electronatoms.ValenceBondTheory(VB)for 1s(1)1s AB1 1s(1)1s AB12121r11s(2)1sABrB1

11s(2)1s(1)d

1s(1)1s(2)11s(2)1s B1 A1 1s(1)1s(2)E1s(2)1s(1)d 1s(1)11s 1s(2)1s

1 E1s1E1s1sA(1)1sB(2)1sA(2)1sBES21SRES2KSHValenceBondTheory(VB)for H11 1S 2J

12ES

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12JJAB2KSKAB 1S *CorrectionErrorsinValenceBondTheory(VB)for Improved 4.SlaterType ComparisonofVBandMOv.s.VB,computational BondLength Dissoc. BondLength Dissoc.Energy Dissoc.Energy VBismuchbetterthanMOincomputingthegroundstateenergyofH2.Fortheelectroncorrelationistakenintoaccountbyexplicitlyincorporatetwoneutral ComparisonofVBandMOMOv.s.VB,excitedT11S (2) 1(2)(2)(2) (2) 121S121S2(1,2)1(1)(2)(2)MOvs.VB:ExcitedT11S(2)1ShowthatVBandMOisidenticalforT1(1,2)1(1)(2)(2)(1)1(1)(2)(2)22思考题VBforMoreDiatomicOnlytheunpairedelectronsOnlytheunpairedelectronswilltakepartinBondH11001100B11C22N33O22F11VBforMoreDiatomic Twovalence O==Close ElectronicComputational 扬扬长避短Comparisonof121 1AA B22

(2) (2) (2) ComparisonofVBand12(2)(2)(2)

2

ComparisonofVBandacbxy x g u g u Eachtermisanelectronconfiguration.SothisschemeiscalledConfigurationIn ction(C.I.,orCI)BondLengthBondLengthDissoc.EnergyComparisonofVBandWhenWhenusingSlatertypeatomicwith=1.17,giv

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