Good morning all researchers
I would like to know , how we can calculate the transient dipole moment on a optimized chemical structure (DFT: Gaussian 09), if possible to give me the keyword permiting to obtain µtr.
Thanks everybody for your help
Hello Mourad Chemek,
Do you want to get the transition dipole moment between the ground state and higher excited states or between excited states? So, it depends what kind of calculation you want to do. The TD-DFT calculations will give you the former, while for the latter, G09 doesn't give you those results but you can use Dalton.
Warm regards,
Somananda
Hello Somananda Sanyal
Thanks a Lots for the response, in my work , Iwould like to calculate the transition dipole moment between the ground state and higher excited states . can you please give me the keyword for the calculation with gaussian 09 (TD-DFT).
For the Dalton is it a free software calculation?
thanks a lots and best regards
For example, using # PBE1PBE/6-31G* TD(nstates=10), you will be able to find transition dipole moment between ground state and the ten calculated excited state from output file, simply searching "Ground to excited state transition electric dipole moments". The data are computed at TD-PBE0/6-31G* level.
Helo Tian Lu
Thanks a Lots for your response, is it possible to do with B3LYP-TD-DFT , or we must do it with TD-PBE0/6-31G*
and other pb, we must choose nstates=10 or it is not an obligation
Best regards
M.Chemek
Of course, you can also use TD-B3LYP level. However, according to many benchmark articles, PBE0 usually performs better for electron excitation problems (For large conjugated systems, especially evident charge-transfer states, there are much better choices, such as CAM-B3LYP and wB97XD).
By default, Gaussian only computes the lowest three excited states. If you are only interested in the first excited state, the default setting is OK. Assume that the highest excited state of interest is x, commonly I suggest setting nstates as i+2.
Thanks Sir for the clearly explication, juste I would like that you clarify two points :
I optimise firstly my structure in the ground state by DFT/B3LYP/6-31G(d) for exple, to calculate the transient dipole moment from ground to excited state, I have to optimise in the excited state by #p opt PBE1PBE/6-31G* TD(nstates=10) , or directly I do a energitic calculation by #p PBE1PBE/6-31G* TD(nstates=10).
Second: This an exemple of how I find in the results folder:
Ground to excited state transition electric dipole moments (Au):
state X Y Z Dip. S. Osc.
1 -0.5398 5.5869 0.0000 31.5048 2.4173
2 1.1836 0.9466 0.0000 2.2970 0.2087
3 0.0000 0.0000 0.0000 0.0000 0.0000
4 0.0000 0.0000 0.0000 0.0000 0.0000
5 0.1707 0.7602 0.0000 0.6070 0.0679
6 0.0000 0.0000 0.0000 0.0000 0.0000
The transient dipole moment is it the value in X, or in Y or in Z or DIP.S,
Thanks a lots for your helpfull
Best regards
M.Chemek
Note that "transient dipole moment" and "transition dipole moment" are very different. If you want to obtain the later, you only need to perform #p PBE1PBE/6-31G* TD(nstates=10)
Transition dipole moment is a vector, therefore it has three components. The Dip.S is simply the sum of square of all the three components.
Good evening Tian
Thanks , it is clear for the transition dipole moment, can you please explain me how to get transient dipole moment, I need to calculate
Best regards
If the "transient dipole moment" you referred to is the transition dipole moment between different excited states, commonly you should optimize structure of an excited state first, then using this structure to conduct a regular TDDFT calculation. However, at TDDFT level, Gaussian can only print transition dipole moment between ground state to excited state, therefore you have to use my code Multiwfn (http://sobereva.com/multiwfn) to calculate the transition dipole moment between various excited states based on Gaussian output file and fch file, see Section 3.21.5 of Multiwfn manual for detail.
Thanks Lots Sir for your clearly response, I wish for your a nice begining week
Best regards
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