excitonic effects

[samaneh]

Dear developers,
As it is printed in the output file of an excitonic transition
we see the weights of each e-h pairs
but I do not know what are their normalization?
would you please explain it, for example for the below output file?

# Electron-Hole pairs that contributes to Excitonic State 2801 more than 5%
#
# Band_V Band_C K ibz Symm. Spin Weight Energy
#
94.0000 114.0000 1.0000 1.0000 -1.0000 0.5491 1.9334
94.0000 113.0000 3.0000 1.0000 1.0000 0.2784 1.9348
94.0000 113.0000 3.0000 3.0000 1.0000 0.2765 1.9348
94.0000 114.0000 2.0000 3.0000 -1.0000 0.1282 1.9099
94.0000 114.0000 2.0000 1.0000 -1.0000 0.1274 1.9099


Thanks in advance

[Daniele Varsano]

Dear Samaneh,
the weight for each exciton i_exc is defined as Acv(i_exc)xAcv(i_exc)* so it should be normalized to 1.
Anyway, if you have two, or more, nearly degenerate excitons, yambo merge the two closed states so in this case the weights will be normalized to 2 in the case of two states and so on....
If you are interested in only one particular state and not let's say, to a peak composed by more excitations, you can reduce the value of the variable Degen_Step, in order to pick just one state.
I suspect that in your case more than one state is considered, probably two.
I realized now that when it happens it is reported in the standard output only as:

Code: Select all

 <01s> :: State 1 Merged with states 1 -> 2

and not in the output file.
We should definitely report this information also in the output.

Best,

Daniele

[samaneh]

Dear Dr. Daniele,

Thank you for your reply.
I search in all report and output files (GW and BSE)
But I could not find these merged states!!
what do you mean by "standard output"??

Best regards
Samaneh

[Daniele Varsano]

Dear Samaneh,
as told you in the previous post this info it is not written in report/output.
Standard output is what appears in your screen when running the executable: so in the l_* files or in the LOG directory when running in parallel. In this case if you run the executable in interactive you will have only on your screen, something like:

Code: Select all

<01s> [01] CPU structure, Files & I/O Directories
 <01s> CPU-Threads:1(CPU)-12(threads)
 <01s> [02] Y(ambo) P(ost)/(re) P(rocessor)
 <01s> [03] Core DB
 <01s> :: Electrons             : 10.00000
 <01s> :: Temperature       [ev]:0.9500E-3
 <01s> :: Lattice factors [a.u.]: 114.0000   20.0000   20.0000
 <01s> :: K points              : 1
 <01s> :: Bands                 : 20
 <01s> :: Symmetries            : 16
 <01s> :: RL vectors            : 194893
 <01s> [04] K-point grid
 <01s> :: Q-points   (IBZ): 1
 <01s> :: X K-points (IBZ): 1
 <01s> [05] CORE Variables Setup
 <01s> [05.01] Unit cells
 <01s> [05.02] Symmetries
 <01s> [05.03] RL shells
 <01s> [05.04] K-grid lattice
 <01s> [05.05] Energies [ev] & Occupations
 <01s> [06] Excitonic Properties
 <01s> :: Sorting energies
 <01s> [07] Amplitude and weights
 <01s> Processing 1 states

<01s> :: State 1 Merged with states 1 -> 2

Code: Select all

 <02s> [08] Game Over

Best,

Daniele