accuracy of sTDA method

[Wei Li]

Hi CP2K forum,

I am trying to calculate the absorption spectrum using LR TDDFT plus sTDA by focusing on one water molecule in a big box.

The sTDA calculation was invoked by the following settings:

       KERNEL sTDA

The use of PBE functional gives negative excited state energy. Then I also included the following in the input:

       &STDA
          FRACTION X

       &END

Here I changed X to several values less than 1. Now the calculation can output positive excited state energy, but still, these tests gave much different results compared to PBE0 result.

Is there a way I can make the PBE/sTDA result better compared to the PBE0 result?

Wei

 

[Jürg Hutter]

Hi

you can shift the virtual states with
EV_SHIFT xxx
in
FORCE_EVAL / PROPERTIES / TDDFPT.

Have a look in the original sTDA papers for some more information.

regards
JH

________________________________________
From: cp...@googlegroups.com <cp...@googlegroups.com> on behalf of Wei Li <liwe...@gmail.com>
Sent: Wednesday, November 15, 2023 8:43 AM
To: cp2k
Subject: [CP2K:19504] accuracy of sTDA method

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[Wei Li]

Dear Prof. Hutter,

Thanks for your answer. One more question:

       &STDA
          FRACTION X
       &END

"FRACTION X", X is the Fock-exchange mixing parameter. 

If I am using sTDA/hybrid functional, X should be set according to the XC fraction of hybrid functional, or not?

But even if I am using PBE functional, I can still set X to different values to get different excited state energies.   

So, it is unclear to me whether the X can be chosen freely when combined with PBE or hybrid functional? Or there are some criteria to set the FRACTION X?

Wei

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