The exchange term in BSE

[sdwang]

Dear all,
When dealing with the system with SOC, how can we obtain the exchange interaction energy after BSE calculation?
Thanks!

Shudong

[Davide Sangalli]

Dear Shudong,
can you better specify what you would like to compute ?

Best,
D.

[sdwang]

Dear Davide,
Thanks for your reply!
I want to obtain the magnitude of the exchange term in the BSE kernel with full spinorial calculations, like in TMDCs system with strong SOC.

Thanks!

Shudong

[Davide Sangalli]

Can you define "the magnitude of the exchange term" with an equation.

In general, when solving the BSE, the exchange kernel enters the excitonic hamiltonian with many matrix elements, K^x_{cvk,c'v'k'} ...
It is not just one number that you can quantify.

One option (but it is just an idea) could be to compare the BSE solution with and without K^x, and see how much the excitonic poles shift in energy.
You can do this with two calculations, one converging the energy cutoff on the exchange and the other setting it to 0.

With exchange (where E_converged can be 10000, 20000, etc ... depending on the material

Code: Select all

BSENGexx = "E_convergend" mHa 

No exchange

Code: Select all

BSENGexx = 0 mHa 

D.