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Re^6: Can't figure out how to find emission spectra of Benzene...

Pavlo Solntsev

On Mon Jun 16 '14 11:00am, Siddheshwar Chopra wrote
>Dear Pavlo,
>Sorry for replying late. I just went through all the files you had provided. I am really grateful to you for taking out time to make us understand this so well. I am really thankful to you.
>Pavlo I checked all the files and would be glad if you could answer some basic questions:

>1) The emission spectra is obtained from the file "pp_opt_s1_tddft.out"?

>2) From S1*--> S1... How to use and understand state tracking? I actually don't understand what I am supposed to do with it. I just know how to turn it on. What happens if I switch it off?

In example i gave you, state tracking probably doesn't matter. However, if you want to relax say state #3 then it may be swapped with other state. In that case state tracking should be turned on. See $TDDFT ISTATE $END description.

>3) You said "1st excited state is B3U"...and used the same optimized coordinates of S0 while optimizing the S1*. Is it right?

Of course it better to start from good coordinates for excited state optimization. The best chose is ground state geometry.

> What should I do with the "1st excited state is B3U"?
Nothing. It is just first excited state of porphyrin.

>This step is very important for understanding. By using the optimized coords. of S0 in optimizing S1*, do you mean that the coordinates of atoms don't change in excited state?
No. Any geometry optimization by definition changes atomic coordinates.

>4) You have used PCM calculations all throughout.. They don't seem time consuming. What all solvents I could use for the same? Do I have acetonitrile available?

Did you check manual? There are two manual available. Th new one and old. Check both of them. CH3CN is available.

>Pavlo until your help, I was in this notion that I should get the most probable orbitals from UV-Vis. calculations and then optimize them for S1 and then obtain the emission spectra. But you haven't talked about most probable orbitals anywhere... Where do I apply the concept I just mentioned then?

Sorry, by i don't understand what you are trying to say within DFT level of theory.

Hope this helps.


>Kind Regards,
>On Thu Jun 12 '14 10:18am, Siddheshwar Chopra wrote
>>Dear Pavel,
>>Your suggestions have always been valuable to me. I will start working on your files and will let you know in case I need your help.

>>Kind Regards,

>>On Wed Jun 11 '14 4:17pm, Pavlo Solntsev wrote
>>>I attached example how to do Luminescence calculation for porphyrin molecule. For more detailed information please, check manual AND this forum.

>>>Salvation model has not been programmed for TDDFT+gradient. Therefore, optimization of the excited state was done without solvent correction. However, this correction was included into spectra calculation.

>>>Very often geometry optimization of the excited state brakes a true molecular symmetry. Keep this in mind.

>>>For more complex systems state of interest may be different, not S1. It is especially true if you have a donor group in your molecule and thus HOMO....HOMO-x belong to the donor, but you are looking for emission within porphyrin core. In such case you need identify the state of interest based on TDDFT(ground state) and knowledge.

>>>Good luck.

>>>On Tue Jun 10 '14 10:16pm, Siddheshwar Chopra wrote
>>>>Dear Alex,
>>>>I searched a lot on this forum regarding the same. What you told is right and I know these too. But I want to step by step how to optimize  the S1? say for  benzene.
>>>>And then how should I determine S0--> S1 (optimized)?
>>>>Please help me stepwise. Any i/p files would be of great help.. I have noted from TDDFT calc of benzene that orbitals 17-24 are most dominant ones. How do I proceed next?

>>>>Kind Regards,

>>>>n Tue Jun 10 '14 7:43pm, Alex Granovsky wrote

>>>>>for emission spectra you need to optimize S1 geometry and then compute
>>>>>vertical transition from S0 to S1 at optimized geometry of S1.

>>>>>Kind regards,
>>>>>Alex Granovsky
>>>>>On Sat Jun 7 '14 9:10pm, Siddheshwar Chopra wrote
>>>>>>Dear Firefly users,
>>>>>>I need some real help in determining the emission spectra (S1--->SO*) of benzene.
>>>>>>I have understood till optimizing the ground state and then obtaining the vertical transition from SO--->S1*...
>>>>>>Please help me now what I should do next? Any i/p files would be welcomed.

>>>>>>Kind Regards,

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