Now, I just declare the number of states by using NSTATE flag. I supposse this flag concerns electronic states. What about vibrational?? The issue is about absorption, I try to determine wavelength of maximum of absorption
Dear Bradley,
great thanks for response, but are you sure that these states are just electronic?? (maybe including also vibrational). Could you suggest another program to do it??
Regards
I don't think any software can do analytical hessian for excited state. But you can try it in Firefly (also called PC-GAMESS) with numerical gradient. This is a free software. Try to ask your question directly on Firefly forum. But if you will do it, please support more information about your system: multiplicity, number of atoms, basis set, level of theory that you need. It's hard to get an advice for such a common question about so hard calculations.
Maciej,
all software use adiabatic approximation and is linear in calculating vibrations. So, You can calculate only ground vibrational state and electronic states independent of it.
Regards,
Eugene.
Eugene,
First, thank you for response.
So, it means that all excitations energies originate just form electronic levels?? If it's true, there is one question: How the absorbtion spectrum is plotted on the base of calculations?? There should be shift between wavelengths from computation and experiment caused by not taking into account oscillations levels.
Regards
Calculating of excited states is the whole problem in quantum chemistry, Maciej, even for electronic states. You can calculate only fragments of absorbtion spectrum if You experienced enough.
Regards,
Eugene.
Thank you again,
I see that, in Poland we say river topic, but Eugen, in my case maximum wavelength is shifted about 30nm for many tautomers. I realise that could be the problem of settings, but I also wonder if it is a problem of not taking into account oscillation levels and unfortunately there is nothing what I can do more??
Regards
No software can solve your problem, Maciej. You must use a priori physical and chemical arguments. It is the art, Maciej.
Regards,
Eugene.
Advice: Compare scales of vibrational and electronic energies.
Also, it may be systematic error in software. Test it on simple objects.
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