Hello. I am analyzing the absorption characteristics of NIR cyanine dyes through TD-DFT calculations.
By the way, I got the following result from the TD-DFT calculation, and I would like to ask for advice on how to interpret it.
The calculation result is as follows
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Gaussian 16 was used, with the calculation settings:
#p td=(singlets,nstates=15) b3lyp/6-311+g(d,p) scrf=(iefpcm,solvent=dichloromethane) nosymm guess=save geom=allcheck polar
Excitation energies and oscillator strengths:
Excited state symmetry could not be determined.
Excited State 1: Singlet-?Sym 1.2706 eV 975.78 nm f=2.4436 =0.000
199 -> 200 0.70885
This state for optimization and/or second-order correction.
Total Energy, E(TD-HF/TD-DFT) = -2550.88173534
Copying the excited state density for this state as the 1-particle RhoCI density.
Excited state symmetry could not be determined.
Excited State 2: Singlet-?Sym 2.2697 eV 546.26 nm f=0.0219 =0.000
198 -> 200 0.51341
199 -> 201 0.48343
Excited state symmetry could not be determined.
Excited State 3: Singlet-?Sym 2.4599 eV 504.01 nm f=0.1044 =0.000
198 -> 200 -0.47864
199 -> 201 0.51181
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I have 3 questions.
1. I know that the values next to the molecular orbital transitions are related with MO contribution. However, what exactly does the minus sign here ( 198 -> 200 -0.47864) mean?
2. The calculation result was obtained that molecular orbital 198 -> 200, 199 -> 201 are involved in the second and third excitation simultaneously, with similar contributions. Is this normal?
S2 f=0.022 H−1 → L (53%), H → L+1 (47%)
S3 f=0.104 H−1 → L (46%), H → L+1 (52%)
I mean, I would like to know whether my calculation results are scientifically "incorrect". (Similar results were obtained in other dyes series I am working on.)
3. How can I get the symmetry of singlet excited state? Are further calculation is needed, such as excited state optimization?
Thanks in advance for reading this long post.
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