Yambo Community Forum

Dear All,

Is it possible to calculate GW corrections for the whole band structure, like Marini, Onida and Del Sole Phys. Rev. Lett. 88, 016403 (2002)?

Thanks
Sincerely, Yunfeng

Yunfeng wrote: Is it possible to calculate GW corrections for the whole band structure, like Marini, Onida and Del Sole Phys. Rev. Lett. 88, 016403 (2002)?

Dear Yungfeng, your question is tricky. I managed to get the full band structure of Cu by using a complicate, ad-hoc interpolation of the GW corrections calculated on a set of high-symmetry points.

You can try to do the same. First calculate the GW corrections on as much high-symmetry points as you can. Then the method I used was to gradually deform the LDA bands in order to match the GW bands calculated on these high-symmetry points. Be careful to impose the GW, interpolated bands to approach the high-symmetry points with zero derivative (as a function of the momentum).

Hope I was hepful

andrea marini wrote:

Yunfeng wrote: Is it possible to calculate GW corrections for the whole band structure, like Marini, Onida and Del Sole Phys. Rev. Lett. 88, 016403 (2002)?

Dear Yungfeng, your question is tricky. I managed to get the full band structure of Cu by using a complicate, ad-hoc interpolation of the GW corrections calculated on a set of high-symmetry points.

You can try to do the same. First calculate the GW corrections on as much high-symmetry points as you can. Then the method I used was to gradually deform the LDA bands in order to match the GW bands calculated on these high-symmetry points. Be careful to impose the GW, interpolated bands to approach the high-symmetry points with zero derivative (as a function of the momentum).

Hope I was hepful

Dear andrea marini,
You said 'calculate the GW corrections on as much high-symmetry points as you can', but in GW calculation, the k-ponit are from the pw scf and nscf file, and this is uniform grids. How can I chose 'as much high-symmetry points as I can'?
S. D. Wang

Dear Yungfeng

converge your GW calculation on a regular grid and the shift it on the points where you need yo calculate GW corrections, as it is explained here:

http://www.yambo-code.org/doc/inputs/ypp_kk.php

Claudio

Dear developers:
I get some QP corrections at some high-symmetry k-poins, but how can I get the 'cond. stretching | val. stretching' as following input file?

QP corrections using a scissor operator and valence/conduction stretching.

scissor | cond. stretching | val. stretching

Dear Yungfeng

in order to get 'cond. stretching | val. stretching' you should fit your GW corrections for
the points you calculated as function of the energy, with a function as:

let's call:
Vs = val. stretching
Cs = cond. stretching
E_homo = top valence bands energy
E_lumo = bottom energy of conduction bands

the scissor operator with stretching is defined as:

for valence bands: E_gw = E_lda + (Vs - 1) * (E_homo - E_lda)
and for conductions: E_gw = E_lda + E_scissor + (Cs - 1) * (E_lumo - E_lda)

check also the file src/qp_ctl/QP_apply_global_stretch.F
to see how it works

Claudio

claudio wrote:Dear Yungfeng

for valence bands: E_gw = E_lda + (Vs - 1) * (E_homo - E_lda)
and for conductions: E_gw = E_lda + E_scissor + (Cs - 1) * (E_lumo - E_lda)

Claudio

I think it should be (E_lda-E_lumo) . Because the E_lumo is the lowest energy in the band, so E_lda larger than it.Am I right?
I noticed in http://www.yambo-code.org/tutorials/Rea ... /index.php,
# K-point Band Eo Eqp E-Eo LDA HF Sc(Eo) Sc(Eqp) Sc`(Eo) Z
#
1.00000 3.00000 0.00000 -2.52528 -2.52528 -22.71821 -30.22404 4.46001 4.98054 -0.20612 0.82910
1.00000 4.00000 0.00000 -2.52208 -2.52208 -22.71822 -30.22392 4.46344 4.98361 -0.20624 0.82902
1.00000 5.00000 9.00799 10.95764 1.94965 -11.07205 -5.98616 -2.89262 -3.13624 -0.12495 0.88893
1.00000 6.00000 19.90535 22.23744 2.33210 -8.85649 -2.74308 -3.40730 -3.78131 -0.16034 0.86180
#
By plotting some of the o-PPA.qp columns it is possible to discuss some physical properties of the LiF QPs. Using columns 3 and 4 we can deduce the band gap renormalization and the stretching of the conduction/valence bands

In the plot, the band stretching is the slope of the fitting lines?