Good day everyone.
I am new to computational chemistry and would like to integrate some part of it in my fluorescence study. I would like to investigate the theoretical fluorescence spectra using TDDFT method in ethanol.
Firstly, I optimized my molecule of interest at the ground state with this command
# opt b3lyp/6-311++g(d,p) geom=connectivity
Then from the output file of above (the optimized version of the molecule), I calculated the energy via TDDFT formalism to determine the absorption spectra. IEFPCM model would be the default version of molecule solvation. Correct me if I am wrong.
# td b3lyp/6-311++g(d,p) scrf=(iefpcm,solvent=ethanol) geom=connectivity
Subsequently, how do I get the fluorescence wavelength/spectra/ data ? Do I rerun from a new optimized version of the molecule since mine was the optimized ground state geometry (S0) ?
Look forward to an in-depth explanation.
Article SYNTHESIS AND SPECTRAL PROPERTIES OF BODIPY LUMINOPHORE WITH...
Dear Nadia,
If you already have the ground state optimized geometry of your compound and you have made an input file out of it for excited state calculations, you could use the following keyword to get a TDDFT optimization in solvent field.
opt td=(direct, nstate=x, root=1)/b3lyp/6-31+g(d,p) scrf=(pcm,solvent=methanol)
This method requests the calculation of x (must be a number) no of excited states in TD-B3LYP level, and optimizes the first excited state only (root=1 keyword), which you need for a simulation of the emission spectrum. The SCRF keyword uses the PCM (Polarizable continuum model) formalism to create a solvent shell of methanol around your fluorophore to give you the desired result.
I hope this helps.
Vladimir Kuzmin and Aniruddha Ganguly , thank you for the answers!
I really appreciate it.
Thank you for the route section example.. I did not know how to optimize the excited state to obtain the theoretical fluorescence wavelength value initially because papers usually do not detail out specific route of the computational part.Will try it out soon.
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