Yambo Community Forum

Dear Daniele,

coming back to one of your previous answer, you told me that in order to get the single value Kx or Kd at q=0 I should compute:

<Psi_lambda | Kx | Psi_lambda>=\sum_cvk \sum_c'vk'' A_lambda^cvk A*_lambda^c'v'k' <cvk|Kx|c'v'k'>.

On the other hand, for q different from zero I don't see where the difference is: I mean, the only thing is to consider k' = k-q isn't it?

Best,
Davide

Dear Davide,

On the other hand, for q different from zero I don't see where the difference is: I mean, the only thing is to consider k' = k-q isn't it?

Yes, for finite q, this is your basis, and these are the elements written in the excitonic matrix.

Best,

Daniele

Dear All,

So I am trying to implement the feature to extract those informations from the ndb.BS_PAR* database. Just a few questions regarding that:

1) What is actually stored in BSE_RESONANT is the whole kernel (i.e. K = Kx + Kd) isn't it? So in order to get the two contributions separately I should do a singlet computation with BSENGexx different from zero from which I get the whole K and a triplet computation with BSENGexx = 0 so that I only get Kd. Then Kx = K - Kd. Is it right?

2) Concerning the size of the database, this is 2500. My computation has 5 valence and 5 conduction bands and 100k points in the whole BZ (which are reduced to 51k points by symmetry). So I assume the size is 5x5x100=2500 and there is no symmetry reduction in the database. Is it correct?

Best,

Davide

Dear Davide,

1) You can do a triplet calculation (Kd only) and an Hartree calculation (Kx only).
2) Yes the matrix is stored in the full BZ.

Best,
Daniele

Dear Daniele,

Thank you for your answer. How do you do a Hartree only (Kx) calculation in BSE?

Best,

Davide

Dear Davide,

just select: Best,

Daniele