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Re^2: Dispersion correction in TDDFT geometry optimizaton calculations?

Thomas Pijper
thomaspijper@hotmail.com


Hello,

As far as I know, that is not correct. Alex' statement is about how DFT-D affects vertical excitation energies and oscillator strengths obtained with TDDFT. Here, there is indeed no use in using DFT-D as the dispersion correction is the same for all energy states. However, for geometry optimizations DFT-D _will_ have an effect -- a geometry optimization for an excited state with and without DFT-D would result in different geometries.

Whether or not DFT-D can be used in the calculation of TDDFT gradients I do not know. This should however be readily visible from the output of the ground state DFT calculation when attempting to perform such a calculation.


Kind regards,
Thom




On Tue Aug 2 '16 2:35am, olgerdovich wrote
------------------------------------------
>On Sat Jul 9 '16 1:10pm, GrEv wrote
>-----------------------------------
>>Hello,

>>I wonder if Grimme's dispersion correction (D3) can be used (can be recommended to use) in TDDFT geometry optimizations? I would appreciate some references to the works where it was used if there are some. Many thanks!

>>Best regards,
>>Evgeniy

>Greetings,
>It appears to me that the answer is "it is of no use": I've accidentally found it in a reply of prof. Granovsky in one old thread (link below) while browsing the forum.

>"As DFT-D correction is the same for all electronic states provided the nuclear geometry is the same, it does not affect vertical excitation energies and in particular TDDFT spectra."

>http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C35e9ea902bHW-8100-45+00.htmhttp://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C35e9ea902bHW-8100-45+00.htm

>Best regard,
>Vladimir Smirnov


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