excitonic weights

[Himani]

Dear sir,

I am trying to understand the excitonic weights output file generated through ypp -e a command. I am not able to understand what "symm." term signifies in the file. Can you please explian me?

Regards,
Himani Mishra
Research Scholar
IIIT Allahabad

[Daniele Varsano]

Dear Himani,
The excitonic wave function is defined as \sum_{cvk}Acvk \phi_vk(rh)\phi_ck(re)
rh,re = hole and electron position
|Acvk|^2 is the weight
c,v= conduction, valence bands
k= k point in the full BZ
In Yambo the k sampling in the Irreducible Bz (IBZ) it is expanded in the full Bz (BZ) by using symmetries, so in the output file a k point in the full BZ is expressed by the corresponding k point in the IBZ and the symmetry operation. The symmetry is indicated by an index and the symmetry corresponding to that index can be found in the firsts lines of any report file.

Best,

Daniele