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Re^2: Doubts regarding TDDFT calculations and excited state determination....

Siddheshwar Chopra

Dear Pavlo,
Thanks for the information Sir. I need some time to understand what you said.  In general,IS THE FIRST EXCITED STATE MENTIONED IN THE TDDFT O/P FILE, THE LUMO ORBITAL?? Please tell me how to analyze the transitions from the excited states from TDDFT o/p file. RIght now I am relying on GAUSSSUM to do that. But I am uncertain. Please help. Please explain in terms of the emission and absorption spectra both. Any simple output file will do.


On Thu Sep 11 '14 5:40pm, Pavlo Solntsev wrote
>On Thu Sep 11 '14 7:21am, Siddheshwar Chopra wrote
>>Dear Firefly Users,

>>I am stuck up with the concept of excited states. Specifically speaking with some doubts in TDDFT.

>>What is meant by NSTATE in FIREFLY i/p file?

>The number of states to be found, excluding the ground state. (Default is 1)

>>I know ISTATE is singlet or doublet...

>The state for which properties and/or the gradient will be calculated. Only one state
>can be chosen. A negative sign may precede the state number; this will enable state
>tracking for the state of interest. (Default is 1)

>When I read the firefly TDDFT o/p file.. I see that for every EXCITED STATE, I have a set of probable transitions... THIS IS WHAT IS CONFUSING ME ...

>What do expect? To see a pure transition from an orbital A to an orbital B? You always have a "contribution" from other transitions. Lets calla them micro-transition. If you have a system where single determinant approach works fine, you should be able to see major component with expansion coefficients close to 0.9.

>>What I assumed till now is that first excited state is LUMO. But now in the firefly o/p file I see HOMO--> LUMO transitions occuring for almost all excited states 1,2,3 etc..

>What about expansion coefficients? Are they the same for all states? If so, you probably have multireference character.

>>So my concept of Excited state is unclear... I just open the TDDFT o/p fie with Gausssum and get the spectra.

>I also get the probabilities of the particular transitions alongwith their osc. strengths. Probabilities must be calculated by squaring and adding the SAPs. But I can't visualize the excited state here. Please explain to me this.

>FF prints all components for transition dipole moment. What does it meant to visualize excited state?

>Also, it would be useful to see the output file.

>>Kind Regards,

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