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Re^2: Geometry optimization of First Excited state.....

Siddheshwar Chopra

Dear Sir,
That means if I have to study UV-Vis Spectra, then studying vertical excitation only, is correct?? If yes then running a CITYP=TDDFT is correct? Is that right? In vertical excitation if the geometry of the molecule (in first excited state???) doesnt change, then optimization still is needed? How time consuming is this job? Does the optimization and oscillator strengths get calculated in the same run RUNTYP=optimize?

Also how do I decide upon studying the adiabatic excitation for my sample?? Say it is a new sample/molecule.. Do you mean phosphorescence transitions by this? Thanks again for explaining so well Sir.

Also is there any way I can comment on radiative or non-radiative nature of transitions?? or can I find electron-phonon interactions using Firefly?


On Tue Apr 1 '14 3:00pm, Amir Nasser Shamkhali wrote
>Dear Sidheshwar
>There are two types of excited states: vertical and adiabatic excited states. Vertical excitation is more important for UV-Vis spectra in which lifetime of excitation is too short in such a way that Franck-Condon effect is important. Thus in vertical excitation, the geometry of the molecule is not changed considerably. TDDFT is appropriate method for vertical excitation. However, in adiabatic excitation, lifetime of excited state is longer and geometry of the molecule is changed. For this excitation you should use configuration interaction (CI) or CASSCF methods.  
>On Tue Apr 1 '14 12:06pm, Siddheshwar Chopra wrote
>>Dear Sir,
>>I went through the forum regarding this but couldn't get my answer exactly. I am running TDDFT calculations on the ground state configuration. Steps were:
>>1) Copied the lowest energy config. coordinates to TDDFT i/p file.
>>2) Using RUNTYP=optimize and CITYP=TDDFT in $CONTRL, to optimize for the first excited state only.
>>Am I performing it in the correct manner? Will I get "Equilibrium geometry located" and the coordinates of Lowest first excited state? Will the same run give me UV-Vis. spectra too?
>>I wish to know how similar is this optimization to the Hessian run, say in terms of the memory and CPU time requirement? How to speed up these calcs?
>>And secondly, I read on the forum about CIS.. But do I need that here?


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