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1、CHAPTER6TransitionMetal-andActinide-ContainingSystemsStudiedwithMulticonfigurationalQuantumChemicalMethodsLauraGagliardiUniversityofGeneva,Geneva,SwitzerlandINTRODUCTIONAbinitioquantumchemistryhasadvancedsofarinthelast40yearsthatitnowallowsthestudyofmolecularsyste
2、mscontaininganyatominthePeriodicTable.Transitionmetalandactinidecompoundscanbetreated12routinely,providedthatelectroncorrelationandrelativisticeffectsareproperlytakenintoaccount.Computationalquantumchemicalmethodscanbeemployedincombinationwithexperiment,topredict
3、apriori,toconfirm,oreventually,torefineexperimentalresults.Thesemethodscanalsopredicttheexistenceofnewspecies,whichmayeventuallybemadebyexperimentalists.Thislatteruseofcomputationalquantumchemistryisespeciallyimportantwhenoneconsidersexperimentsthatarenoteasytohand
4、leinalaboratory,as,forexample,explosiveorradioactivespecies.Itisclearthatagoodunderstandingofthechemistryofsuchspeciescanbeusefulinseveralareasofscientificandtechnologicalexploration.Quantumchemistrycanmodelmolecularpropertiesandtransformations,andinReviewsinCompu
5、tationalChemistry,Volume25editedbyKennyB.LipkowitzandThomasR.CundariCopyrightß2007Wiley-VCH,JohnWiley&Sons,Inc.249250TransitionMetal-andActinide-ContainingSystemscombinationwithexperiment,itcanleadtoanimprovedunderstandingofprocessessuchas,forexample,nuclearwaste
6、extractionandstorageproce-duresforradioactivematerials.Quantumchemistshavedevelopedconsiderableexperienceovertheyearsininventingnewmoleculesbyquantumchemicalmethods,whichinsomecaseshavebeensubsequentlycharacterizedbyexperimentalists(see,forexample,Refs.3and4).The
7、generalphilosophyistoexplorethePeriodicTableandtoattempttounderstandtheanalogiesbetweenthebeha-viorofdifferentelements.Itisknownthatforfirstrowatomschemicalbondingusuallyfollowstheoctetrule.Intransitionmetals,thisruleisreplacedbythe18-electronrule.Upongoingtolanth
8、anidesandactinides,thevalencefshellsareexpectedtoplayarole.Inlanthanidechemistry,the4fshelliscontractedandusuallydoesnotdirectlyparticipateintheche-micalbondin