I want to obtain the screened Coulomb interaction matrix elements like the ones in BSE kernel with the generalization to all bands, not limited to electron-hole states. I used the so-called non-equilibrium (NEQ) GW implemented in real-time Yambo as explained in Dr. Andrea Marini's paper. However, I found the output matrix elements are too small (around one magnitude smaller) compared to those from BSE kernel calculations. By comparing these two calculations and looking into the codes:
https://github.com/yambo-code/yambo/blo ... W_static.F
https://github.com/yambo-code/yambo/blo ... rnel_std.F
I realize a missing factor of 4pi in NEQ GW calculations, while there is an additional factor of 4pi at the line of 90 in the file
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K_correlation_kernel_std.F
After adding this 4pi into NEQ GW calculations and removing the line 172 of the file
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COLLISIONS_NEQ_GW_static.F
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if (iqibz==1) EM1s(1,1)=X_mat(1,1,1)*sqrt(isc%gamp(1,1)/DL_vol/real(q%nbz,SP))
My question is: what is the role of the line 172?
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if (iqibz==1) EM1s(1,1)=X_mat(1,1,1)*sqrt(isc%gamp(1,1)/DL_vol/real(q%nbz,SP))
Thanks a lot,
Changpeng