Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly

Jonas Baltrusaitis
jonas-baltrusaitis@uiowa.edu

Maybe I am not interpreting right: all I need is emission spectrum. So I do not have particular bonds or orbitals in mind, I only need to optimize to certain excited state or averaged states to get decent representation of fluorescence spectra. Does that change anything or I still have to select bond or orbital wise?

Also, would that make these calculations state specific or state average?

Jonas


On Wed Jul 28 '10 6:35pm, Jim Kress wrote
-----------------------------------------
>Try doing a NBO analysis.  Then select your active space from the set of NBOs (or even NLMOs) that correspond to the atoms and/or bonds of primary concern to you.

>This is how I usually set-up my MCSCF/ CASSCF calculations.

>Jim

>On Wed Jul 28 '10 3:15am, sanya wrote
>-------------------------------------
>>On Tue Jul 27 '10 4:16pm, Jonas Baltrusaitis wrote
>>--------------------------------------------------
>>>From what I've read in the literature CASSCF should be a good thing for my molecules since it can deal with multireference character and bond breaking. I am a bit hesitant since I am not sure how to select the active space. Would TDDFT do in selecting which orbitals and electrons to correlate? Is there a rule of thumb?

>>DFT (as well as HF) orbitals are not very good as starting MOs. Natural orbitals are better. Unfortunately, there is no rule of thumb in selecting the active space, just a common sense and a chemical insight :) In fact, it is individual for each molecular system.

[ This message was edited on Thu Jul 29 '10 at 4:49am by the author ]