I'm doing TDDFT calculation. I have calculated excited state calculation for n=20 states. The first state (lowest in energy) showing negative wavelength and oscillator strength. How we can explain it and what does it mean?
Qabas M. Alkhatib, the negative wavelength indicates that the structure is not optimized properly and it is like a transition state. Do the optimization again and then do the TDDFT.
You can only find a negative transition energy probably there is a state lower in energy than that your reference state (i.e., you are getting emission rather than an absorption). Though, I do not know what functionals you are using, this may be due to the use of a functional that is not appropriate for excited state calculations. Change the functional, hopefully, it will be resolved.
Hallo, Qabas!
The negative wavelength means that you are not in the lowest state. This happens if your SCF procedure did not converge to the same state as in the previous job with geometry optimization (usually if you do not use .chk file for restarting the TDDFT job). You must check the stability of your wavefunction (keyword Stable in Gaussian).
Another reason might be in using different DFT functionals in geometry optimization job than in the TDDFT one.
Best wishes
mb
Hi, Qabas
Martin Breza Snehasis Banerjee Suranjan Shil gave good suggestions or answers.
You should check these wavelengths by comparing with the experimental data.
Do you have one molecule or not?
because of the change in the dipole moment direction may shows a negative value. also the intersection cross.
maybe this is fluorescence case!
You should give more detail about your structure.
- Badges
- Science topic