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

Siddheshwar Chopra

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??

2) Regarding B3U.. i used gausssum... with no symmetry constraint...

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?

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?

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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