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Re^9: Can't figure out how to find emission spectra of Benzene...

Pavlo Solntsev

On Fri Jun 20 '14 1:01pm, Siddheshwar Chopra wrote
>Dear Pavlo,
>Thanks for the useful answers. I have some points:
>1) I will then keep the state tracking on always. however I dont know how to track this flipping of states manually. I came to know of tdprp=.t., to get excited state properties. Is it good to try??

There is no option to track a state manually, AFAIK. About TDPRP, it is always good to try.

>2) Regarding B3U.. i used gausssum... with no symmetry constraint...
gausssum is basically a wrap for cclib. It reads information from you output file. In you output file your molecule has C2 symmetry.

>3) Thanks for the
>4) regarding mcscf one... Pavlo I am actually interested in fluorescence only... so I think state tracking won't be essential in my case.. what do u say?

It is important for geometry optimization of an excited state. Different systems, different situation. I know system where you have to optimize state #17 to get luminescence.

>5) One most important question to u: Is it the same way I should check for imaginary frequencies for the S1* state, like we do for S0?? I must run hessian for every optimization right?

Technically- yes.

>kind Regards,

>On Tue Jun 17 '14 2:58pm, Pavlo Solntsev wrote
>>On Tue Jun 17 '14 1:25pm, Siddheshwar Chopra wrote
>>>Dear Pavlo,
>>>I really appreciate all your help. Your guidance has helped me a lot always.
>>>Sir, regarding you replies:
>>>1) regarding state tracking... do you mean to say if i m studying singlet to singlet transition, then it is not necessary??
>>No.It just help you to track (watch) the state of interest if order of states changes during the geometry optimization. I believe the optimization of triplet state should be the same as singlet.

>>>In general can I take it as a rule of thumb to switch it on always?? Like you did..
>>>I just need to add - sign to activate it..and then i dont need to bother about anything else right??
>>It is make sense for geometry optimization only. Yes, it is safe to leave it on.

>>>2) I understood about using optimized coords. Of S0 for S1*.. thnx for that..
>>>But how did you know B3U is first excited state? I checked my o/p file with gausssum.I couldn't get that information.. i could only find A and B..
>>What is the point group of porphyrin? Gaussian used C2 group. It is problem with Gaussian.

>>>3) Regarding PCM... i checked 8.0.x manual.. but couldnt find the list of solvents.. :-(

>>>4) Pardon me about the last one... I am unsure about it as I read in this forum that active space is created.. yes it is not is MCSCF/XMCQDPT2...
>>>I just wish that the procedure you have told me will be the best suited for my needs.. :-)
>>>Pavlo following the same procedure, I can get singlet to either singlet or triplet transitions/emission spectra..right? But then for downward transitions, the gnd state multiplicity will change..
>>Probably it is correct to talk about phosphorescence. If you optimized triplet state and then looking for transition to a singlet.


>>>Kind Regards,
>>>On Mon Jun 16 '14 9:18pm, Pavlo Solntsev wrote
>>>>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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