第16讲：-G1-G2-G3-理论

G1,G2,G3理论一、G1和G2理论(1)J.A.Pople,M.Head-Gordon,D.J.Fox,K.RaghavachariandL.A.Curtiss,J.Chem.Phys.90,5622(1989).(2)L.A.Curtiss,C.Jones,G.W.Trucks,K.RaghavachariandJ.A.Pople,J.Chem.Phys.93,2537(1990).(3)L.A.Curtiss,K.Raghavachari,G.W.TrucksandJ.A.Pople,J.Chem.Phys.94,7221(1991).1.L.A.Curtiss,K.Raghavachari,P.C.Redfern,V.Rassolov,andJ.A.Pople,JournalofChemicalPhysics,109,7764(1998).2.L.A.Curtiss,P.C.Redfern,K.Raghavachari,V.Rassolov,andJ.A.Pople,JournalofChemicalPhysics,110,4703(1999).3.A.G.Baboul,L.A.Curtiss,P.C.Redfern,andK.Raghavachari,JournalofChemicalPhysics110,7650(1999).G3Theory基本理论一些计算方法的复合运算G2理论的主要步骤：第一步：HF/6-31G(d)优化分子几何构型，并用振动分析确认其为平衡几何构型以及得到ZPE,0.8929第二步：用以上得到的最后结构参数用MP2(full)/6-31G*重新优化分子几何构型，以后就用该几何构型做计算。第三步：计算一个基本的能量Ebase,MP4/6-311G(d,p)能量，事实上该能量从第六步计算中得到。第四步：对基本能量加弥散基组得到E+,E[MP4/6-311+G(d,p)]-Ebase第五步：对重原子考虑更高的极化函数，E2df,E[MP4/6-311G(2df,p)]-E[MP4/6-311G(d,p)]第六步：EQCIE[QCISD(T)/6-311G(d,p)]-Ebase第七步经验估计其它基组上的缺陷EHLC-0.00019n-0.00595nEG1=Ebase+E++E2df+EHLC+ZPE第八步：计算MP2/6-311+G(3df,2p)能量G2=(+2df-+-2df)+3d2p+2df=E[MP2/6-311+G(2df,p)]-E[MP2/6-311G(d,p)]+=E[MP2/6-311+G(d,p)]-E[MP2/6-311G(d,p)]2df=E[MP2/6-311G(2df,p)]-E(MP2/6-311G(d,p)]3d2p=E[MP2/6-311+G(3df,2p)]-E[MP2/6-311+G(2df,p)]G2=EStep8-EStep5(MP2)-EStep4(MP2)+EStep3(MP2)第九步：HLC=0.00114nEG2=EG1+G2+HLCG3MP2LARGE用B3LYP/6-31G(d)几何构型和振动濒率A.G.Baboul,L.A.Curtiss,P.C.Redfern,andK.Raghavachari,J.Chem.Phys.110,7650(1999).GAUSSIANJOBS•对于平衡几何构型：＃pG2H2o01HO1r1H2r11a1R1=1.04A1=104.5过渡态＃pG2opt=(ts,noeigentest,nrscale,calcfc)iop(1/8=6)TS01HC1r1N2r21a1R1=1.25R2=1.26A1=67.0KeywordsG1G2G2MP2G3G3MP2G3B3G3MP2B3G2(0K)Zero-point-correctedelectronicenergy:E0=Eelec+ZPEG2EnergyThermal-correctedenergy:E=E0+Etrans+Erot+EvibG2EnthalpyEnthalpycomputedusingtheG2predictedenergy:H=E+RTG2FreeEnergyGibbsFreeEnergycomputedusingtheG2predictedenergy:G=H-TSexaples•G2forwatermolecule•G3B3forwatermoleculeJournalofChemicalPhysics126084108(2007).Gaussian-4theory1isthefourthinaseriesofGxmethodsforcalculationofmolecularenergies.Itisacompositetechniqueinwhichasequenceofwell-definedabinitiomolecularorbitalcalculationsisperformedtoarriveatatotalenergyofagivenmolecularspecies.GeometriesaredeterminedusingB3LYPdensityfunctionaltheorywiththe6-31G(2df,p)basisset[6-31G(2fg)forthird-rownontransitionmetalelements).Zero-pointenergiesarealsocalculatedwiththisbasisset.CorrelationlevelcalculationsaredoneusingMoller-Plessetperturbationtheoryuptofourth-orderandwithcoupledclustertheory.Largebasissets,includingmultiplesetsofpolarizationfunctions,areusedinthecorrelationcalculations.ThreebasissetsthatareusedinG4theoryareavailableonthiswebsite.ThesearetheG3LargeXPbasisusedintheMP2(FU)stepandtwobasissets(quadrupole-zetaandquintuple-zeta)usedforextrapolationtotheHartree-Focklimit.Thelattertwoarederivedfromcorrelationconsistentbasissets.ＨＬＭｅｔｈｏｄ