PBE0+GW for 2D materials

[HaozheLi]

Dear Yambo developers,

I want to use yambo to do PBE0+GW calculations for some 2D materials.

Before going to Yambo, we have to do the scf and nscf calculations in QE using PBE0. And we have to set many parameters, such as exxdiv_treatment and x_gamma_extrapolation. I found this suggestion in the Yambo official website:

In order to have meaningful results, you must treat the divergences of the exchange part in QE and Yambo on the same footing (vcut_spherical or vcut_ws in exxdiv_treatment for QE and CUTGeo=”sphere or ws” respectively in YAMBO)

My question is: if I want to use CUTGeo='slab z' treatment in Yambo after the QE calculations, how should I set these parameters in QE to get reasonable results? Could you please give me some advice for QE and Yambo calculations?

Best wishes,
Haozhe

[Daniele Varsano]

Dear Haozhe,

you can try to set "gygi-baldereschi" in QE, but in this case the treatment of the divergency is different and you can have some systematic error.
As you reported, the safest way is to use vcut_ws in QE and "ws" in Yambo. The method is accurate as long as you check the convergence with respect the k point mesh.

Best,
Daniele

[HaozheLi]

Dear Daniele,

Thanks for your reply.
I have two questions:

1. If I use vcut_ws in QE and "ws z" in Yambo, I can not use the powerful tool "RIM-W" anymore, right? And I have to do the convergence test with respect the k point mesh.

2. Using "ws z" in Yambo, I need not to set CUTBox anymore, just like "slab z", right?

Best wishes,
Haozhe

[Daniele Varsano]

Dear Haozhe,

1) Unfortunately, you cannot use the RIM-W as it is specialized for the slab cutoff
2) You do not need to use CUTBox, but CUTGeo="ws z".

Best,
Daniele