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1、Volume211,number2,3CHEMICALPHYSICSLETTERS13August1993AnefficientalgorithmforelectronrepulsionintegralsovercontractedGaussian-typefunctionsSeiichiroTen-noDepartmentofChemistry,FacultyofScience,KyoioUniversity,Kitashirakawa,Sukyo-ku,Kyoto606,JapanReceive
2、d4JuneI993Anefficientnewalgorithmfortwo-electronrepulsionintegrals(ERIs)overcontractedCartesianGaussian-typefunctionshasbeenproposed,makinguseofthecontractedrecurrencerelation(CRR)derivedhere.TheCRR,whichisobtainedbyextendingtheauxiliaryfunction-basedm
3、ethodologies,enablesustoremoveallthetransformationstoincrementangularmomentumofERIsfromthecontractionloops.ThenewschemeturnsouttobeverysuitableforcontractedERIs.Explicitflop(floatingpointoperation)countsindicateabout60%reductionofcomputationalworkinthe
4、innermostcontractionloopfor(ppIpp)and(sp)”ERIclasses,comparedtotherecentschemeofGill,Head-GordonandPople.1.IntroductionisuniquelydefinedbyitsangularmomentumvectorGenerationandmanipulationoftwo-electronre-a=(a,,uY,a,),byitspositionvectorAandbyitspulsion
5、integrals(ERIs)arethemajorcomputa-exponentck.TheevaluationofcontractedERIs,viz.,tionaltasksinabinitioquantum-chemicalcalcula-linearcombinationsofERIsoverprimitiveGTFs,istionsofmolecularelectronicstructure,becausethequitetime-consumingevenformodesdegree
6、sofnumberofintegralsincreasesasthefourthpowerofcontraction.Moreefficientalgorithmsforcon-thesizeofthebasisfunctionsused.OnepromisingtractedERIsaswellasprimitiveERIsaredesiredforwaytoreducethenumberofERIsassembled,es-anyrealisticapproachinthetheoretical
7、studyoflargepeciallyintheHartree-Fock(HF)approximation,systems.istoemploycontractedGaussian-typefunctionsRecently,Gill,Head-GordonandPople(GHP)(GTF,whichwerefirstproposedasbasisfunctions[21suggestedanewschemecombiningthebestfea-byBoys[1]andarenowwidely
8、inuse).Theinner-turesofthemethodsbyHead-GordonandPopleshellorbitals,whichremainessentiallyatomicin(HGP)[31andbyMcMurchieandDavidson(MD)characterforordinarychemicalinterests,canbeap-[41,utilizingtwo-centerintermediariesofprimitiveproxima
