[gpaw-users] singlet-triplet transition in GPAW tddft

[Michael Walter]

Dear Ivano,

2017-02-03 10:30 GMT+01:00 Ivano E. Castelli <ivano at chem.ku.dk>:

> Dear Dr. Michael Walter.
>
> My name is Ivano Castelli, I am a post doc in Jan Rossmeisl group at
> Copenhagen University.
> I am currently working on calculating spin singlet-triplet transitions in
> radicals like carboxylic acids using GPAW.
> I have found a paper of yours where you used the TDDFT module implemented
> in GPAW to calculate these singlet-triplet transitions (
> http://dx.doi.org/10.1063/1.2943138).
> I have followed the instructions here: https://wiki.fysik.dtu.dk/gpaw
> /exercises/lrtddft/lrtddft.html but in the output of the calculation I
> cannot see when the transition is singlet-triplet for example when I
> calculate the excitation energies for CO as shown here:
> http://www.psi-k.org/newsletters/News_98/Highlight_98.pdf
> I was wondering if you can help on this matter.
>

The simplest approach is:

1. to calculate CO spin paired, this will give you the singlets only.
2. Then you force spin (spinpol=True in the ground state calculation) and
you'll get both singlets and triplets. So, the triplets are the ones
missing in 1.

There are also other possibilities starting from 2:

3. The LrTDDFT object has a function "singlets_triplets" that should give
you both separated. I think it works and is tested, but better check
against 1+2 above.
4. Use the vanishing oscillator strength as a hint for triplets and
use LrTDDFT.analyse() for the Kohn-Sham contributions.

I'm painfully aware that the documentation could be improved to explain
these things and would be very happy, if you could help on this matter.

Best,
Michael



>
> Thank you in advance,
> best regards,
> Ivano
>
> --
> Ivano E. Castelli
> Postdoc
>
> Department of Chemistry
> University of Copenhagen
> Universitetsparken 5
> Building D, room S04
> DK-2100 Copenhagen Ø
> ivano at chem.ku.dk
> +45 53538491
>
>


-- 
------------------------------------------
PD Dr Michael Walter
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