[DFTB-Plus-User] question about transition weights in EXC.DAT files

[Benjamin Hourahine]

Hello Mostafa,

The TD-DFTB excitation is expanded out as excitations between the Kohn-Sham like single particle states. In some cases only one of these transitions dominates (weight 1), but often there are multiple single particle transitions that contribute to the resulting many body excitation transition of the system (so the weight would be less than 1). A weight of 1 means the excitation is single particle-like in character (i.e. the RPA approximation would give its energy) but less than 1 means it is a more collective transition involving (several) single particle transitions.

Regards

Ben

On 22/10/2019 06:15, Mostafa Tavakoli wrote:
Hi
Can anybody please tell me what are "weight"s reported in EXC.DAT files?. I read the manual and the only thing found there was that weight=1 means we have primarily transitions. I want to know the physical meaning of weights and that what do weights smaller than 1 mean?
Thank you very much.



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        Dr.  B.  Hourahine,  Senior  lecturer
            SUPA, Department  of  Physics,
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