Question related to cohsex gw calculation

[Bramhachari Khamari]

Dear Developers,

I would like to learn the cohsex gw calculation using version 5.0. With the command line option yambo -gw0 c following input is produced. T

gw0 # [R] GW approximation
cohsex # [R][Xp] COlumb Hole Screened EXchange
dyson # [R] Dyson Equation solver
HF_and_locXC # [R] Hartree-Fock
em1s # [R][Xs] Statically Screened Interaction
dipoles # [R] Oscillator strenghts (or dipoles)
EXXRLvcs= 69697 RL # [XX] Exchange RL components
VXCRLvcs= 69697 RL # [XC] XCpotential RL components
Chimod= "HARTREE" # [X] IP/Hartree/ALDA/LRC/PF/BSfxc
% BndsRnXs
1 | 300 | # [Xs] Polarization function bands
%
NGsBlkXs= 1 RL # [Xs] Response block size
% LongDrXs
1.000000 | 0.000000 | 0.000000 | # [Xs] [cc] Electric Field
%
XTermKind= "none" # [X] X terminator ("none","BG" Bruneval-Gonze)
GWoIter=0 # [GW] GWo self-consistent (evGWo) iterations on eigenvalues
GWIter=0 # [GW] GW self-consistent (evGW) iterations on eigenvalues
%QPkrange # [GW] QP generalized Kpoint/Band indices
1|19|1|300|


i) Tag related to GbndRnge is missing. What command should I use to get the proper input.
% GbndRnge
| | # [GW] G[W] bands range
%

ii) If I want to continue to do the real time simulation after the cohsex gw
a)Do I need to do collision part ?
b) which HXC potential should I use?

Regards

[Daniele Varsano]

Dear Bramhachari,

coshex self-energy can be expressed in a way involving occupied states only, so you do not need that variable.
You can force the code to use the expression involving empty states by adding the variable (UseEbands), but this done mostly for
validation and debugging purpose.

About the realtime simulation, I'm not expert on that, others will answers.

Best,
Daniele

[Bramhachari Khamari]

Dear Sir,
Thanks a lot for the reply.

Regards,

[Davide Sangalli]

ii) If I want to continue to do the real time simulation after the cohsex gw
a)Do I need to do collision part ?
b) which HXC potential should I use?

If you want to perform TD-HSEX simulations:
a) yes
b) "HARTREE+SEX"

Notice that the COH part is not updated in the real-time simulation, since the screening is kept frozen at the equilibrium value (same as in BSE)

You can load the previously computed QP corrections, which can be COHSEX or even GW (same as in BSE)

Best,
D.

[Bramhachari Khamari]

Dear Sir,
Thank you for the reply. Can you clarify whether the following statements are correct

i) In case of COHSEX, screening does not change with time
ii) If I use GW and proceed for the real time simulation then screening changes with time.

Regards,