考慮溶劑效應(yīng)的紫外吸收光譜計(jì)算

1、采用采用PCM模型計(jì)算溶液中的紫外吸收光譜模型計(jì)算溶液中的紫外吸收光譜ThePCMmethodinGaussian09includesanexternaliterationprocedurewherebytheprogramcomputestheenergyinsolutionbymakingthesolventreactionfieldselfconsistentwiththesoluteelectrostaticpotential(

2、thelatterbeinggeneratedfromthecomputedelectrondensitywiththespecifiedmodelchemistry).Step1:Groundstategeometryoptimizationfrequencies(equilibriumsolvation平衡溶劑化：在電子結(jié)構(gòu)不發(fā)生改變時(shí)，若分子幾何結(jié)構(gòu)發(fā)生變化則平衡溶劑化：在電子結(jié)構(gòu)不發(fā)生改變時(shí)，若分子幾何結(jié)構(gòu)發(fā)生變化則溶劑也跟著變

3、化溶劑也跟著變化).ThisisastardOptFreqcalculationonthegroundstateincludingPCMequilibriumsolvation.獲得溶劑中基態(tài)穩(wěn)定幾何結(jié)構(gòu)，默認(rèn)為Eq狀態(tài)%chk=01ac#B3LYP631G(dp)OptFreqSCRF=(Solvent=Ethanol)Acetaldehydegroundstate01分子說(shuō)明(請(qǐng)自行補(bǔ)充)Hereistheenergyofthegr

4、oundstateoptimizedgeometryinsolution:SCFDone:E(RB3LYP)=153.851761719A.U.after1cyclesStep2:Verticalexcitationwithlinearresponsesolvation.默認(rèn)為NonEq過(guò)程ThisisaTDDFTcalculationoftheverticalexcitationtherefeatthegroundstateequil

5、ibriumgeometrywiththedefaultsolvation:linearresponsenonequilibrium.WeperfmasinglepointTDDFTcalculationwhichdefaultstononequilibriumsolvation.Theresultsofthisjobwillbeusedtoidentifywhichstatestatesareofinteresttheirdering

6、.Theseresultsgiveareasonabledeionofthesolvationoftheexcitedstatebutnotquiteasgoodasthatfromastatespecificsolvationcalculation.Inthiscaseweseethatthen→πstate(產(chǎn)生第一激發(fā)態(tài)的躍遷方式)isthefirstexcitedstate.Nextwewillusethestatespecif

7、icmethodtoproduceabetterdeionoftheverticalexcitationstep.復(fù)制以上step1中的01ac.chk并將復(fù)制文件命名為02ac.chk，然后執(zhí)行如下操作計(jì)算紫外躍遷吸收光譜。下邊這個(gè)計(jì)算默認(rèn)為nonequilibriumsolvation。垂直激發(fā)默認(rèn)為NonEq過(guò)程，但此時(shí)沒(méi)有使用EI%chk=02ac構(gòu)全同，沒(méi)有改變。3.2的能量減去3.1的能量即為帶有溶劑效應(yīng)矯正后的紫外吸收光譜

8、。復(fù)制01ac.chk文件，并將復(fù)制后文件重新命名為03ac.chk。執(zhí)行如下計(jì)算%chk=03ac#B3LYP631G(dp)SCRF=(Solvent=EthanolRead)Geom=CheckGuess=ReadAcetaldehyde:preparefstatespecificnoneqsolvationbysavingthesolventreactionfieldfromthegroundstate01NonEq=write

9、link1%chk=03ac#PB3LYP631G(dp)SCRF=(Solvent=EthanolExternalIterationRead)Geom=CheckGuess=ReadTD(NStates=6Root=1)Acetaldehyde:readnoneqsolvationfromgroundstatecomputeenergyofthefirstexcitedwiththestatespecificmethod01NonEq

10、=readHereistheenergyoffirstexcitedstate—atthegroundstateoptimizedgeometry—fromthenonequilibriumsolvationstatespecificcalculation:AfterPCMcrectionstheenergyis153.687679826a.u.Subtractingthisenergyfromthegroundstateenergy(

11、fromstep1)givesthegroundstatetofirstexcitedstateabsptionincludingthestatespecificsolvationcrection:at277.69nm.計(jì)算溶劑中的激發(fā)吸收光譜??！ExternalIteration方法方法(EI方法方法)的大致含義是：不同于之前常用的標(biāo)準(zhǔn)方法(標(biāo)準(zhǔn)方法中計(jì)算溶劑效應(yīng)時(shí)先采用SCF方法獲得初步結(jié)果，然后把溶劑效果當(dāng)做微擾項(xiàng)疊加到體系中獲得

12、體系性質(zhì))，EI方法直接針對(duì)溶劑體系的MP2結(jié)果獲得溶劑效果，讓溶質(zhì)自洽于環(huán)境溶劑。問(wèn)題，若在3.2中，去除SCRF=EI關(guān)鍵詞，則能量數(shù)值有多大變化，激發(fā)波長(zhǎng)有多大變化？若能量數(shù)值和激發(fā)波長(zhǎng)均不變，則表示對(duì)光譜結(jié)果數(shù)據(jù)沒(méi)有影響，這樣就不叫statespecificsolvationcrection了。所以我想應(yīng)該是變化了。若變化了，一次只能使用ROOT=N計(jì)算第N個(gè)激發(fā)的具體波長(zhǎng)，每次激發(fā)單獨(dú)計(jì)算，這樣很費(fèi)事。但我們可以計(jì)算振動(dòng)系數(shù)比