Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly

Jim Kress
jimkress_35@kressworks.com

Look here for more info:

http://www.chem.wisc.edu/~nbo5/

Jim

On Thu Jul 29 '10 4:49am, Jonas Baltrusaitis wrote
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>I got similar suggestion from Sanya only he suggested natural orbitals of interest.

>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
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>>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
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>>>On Tue Jul 27 '10 4:16pm, Jonas Baltrusaitis wrote
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>>>>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.