Solvation and excited states2022
Solvation and excited states 2022
Implicit solvation modelSolvent is treated as a polarizable continuum with a dielectric constant, instead of explicit solvent molecules. Models include: Onsager (ScRF), PCM,IEFPCM,SMD,etc.Keywords: scrf=XX. E.g. scrf=SMD, IEFPCM...国SCRF(SMD, solvent=chloroform), set SMD solvation model usingchloroformas the solvent.SinglepointwithSMD:ethanol inwater#pm052x/6-31g(d)scrf=(smd,solvent=water)Gas phase:-154.99982361Inwater:-155.00785401Solvation free energy:627.51*(-155.00785401-(-154.99982361))=-5.04kcal/mol
Solvent is treated as a polarizable continuum with a dielectric constant, , instead of explicit solvent molecules. Models include: Onsager (SCRF), PCM, IEFPCM, SMD, etc. ⚫ Keywords:scrf=XX. E.g. scrf=SMD, IEFPCM. ⚫ SCRF(SMD, solvent=chloroform), set SMD solvation model using chloroform as the solvent. #p m052x/6-31g(d) scrf=(smd,solvent=water) Gas phase: -154.99982361 In water: -155.00785401 Solvation free energy: 627.51*(-155.00785401-(-154.99982361) )= -5.04 kcal/mol. Implicit solvation model Single point with SMD: ethanol in water
Excitedstatesand UV-VisspectraExcitedstatesmethodssupported inGaussian:CiS-type(ZINDO, CIS,TDHF, TDDFT), EOM-CCSD, CASSCF, etcGeneralsetupforCiS-typecalculation:nstates=N, compute N excited statessinglet, all thecomputed states are singlet states.triplet, all the computed states are singlet states.50-50, half are singlet and half are triplet states.GasphaseTDDFT:UV-Visspectraofbiphenyl1.Ground state geometry optimization#P opt PBE1PBE/6-31g(d)2. Use the optimized structure, compute itsexcitedstates#P PBE1PBE/6-31g(d) TD
Excited states methods supported in Gaussian: CIS-type (ZINDO, CIS, TDHF, TDDFT), EOM-CCSD, CASSCF, etc. General setup for CIS-type calculation: ⚫ nstates=N, compute N excited states. ⚫ singlet, all the computed states are singlet states. ⚫ triplet, all the computed states are singlet states. ⚫ 50-50, half are singlet and half are triplet states. 1. Ground state geometry optimization #P opt PBE1PBE/6-31g(d) 2. Use the optimized structure, compute its excited states #P PBE1PBE/6-31g(d) TD Excited states and UV-Vis spectra Gas phase TDDFT: UV-Vis spectra of biphenyl
Results---UV-ViSX口G1:M1:V1-ElectronicSpectraPlotsAUV-VISSpectrum0.5020000180000.45Oscillator160000.40140000.35UO0.30寸120000.2510000北LS0.20品80000.1560004000-0.102000-0. 050-0.00TTTTTTTTT340320200180300280260240220160140(nm)Excitation EnergyVExcitationEnergy(nm)=239.87,OscillatorStrength=0.4697SearchOscillatorExcitation energies and oscillatorstrengths:Excitation energyOscillatorstrengthExcited statel:singlet-B5.1688eV.239.87nmf=0.4697<S**2>=000041->420.69436Transition orbitalThis state for optimization and/or second-order correction-462.560287294Excited stateenergy=excitationTotal EnergY,E(TD-HE/TD-KS)=Copying the excited state density for this statenergy + ground state ehergy
Results-UV-VIS Search Oscillator Transition orbital Excitation energy Oscillator strength Excited state energy = excitation energy + ground state energy
Exercises1. Using the model chemistry of M052x/6-31g(d), compute thesolvationfreeenergyof ethanolinbenzene.2. Compute the UV-Vis spectra for alizarinGeometry optimization: #p opt PM6Excitation:# TD(nstates=30) PBE1PBE/6-31g(d)0OHOH0
1. Using the model chemistry of M052X/6-31g(d), compute the solvation free energy of ethanol in benzene. 2. Compute the UV-Vis spectra for alizarin Geometry optimization: #p opt PM6 Excitation: # TD(nstates=30) PBE1PBE/6-31g(d) Exercises