Question related to cohsex gw calculation

You can post here problems arising when using the latest 5.0 reslease of Yambo. Issues as parallelization strategy, performance issues and other technical aspects realted to the new release.

Moderators: Davide Sangalli, andrea marini, Daniele Varsano, andrea.ferretti, myrta gruning, Conor Hogan

Post Reply
Bramhachari Khamari
Posts: 69
Joined: Wed Oct 23, 2019 5:52 am

Question related to cohsex gw calculation

Post by Bramhachari Khamari » Sat Feb 20, 2021 11:12 am

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
Bramhachari Khamari
Post Doctoral Fellow
Department of Physics
IIT Kanpur, India.

User avatar
Daniele Varsano
Posts: 2723
Joined: Tue Mar 17, 2009 2:23 pm
Contact:

Re: Question related to cohsex gw calculation

Post by Daniele Varsano » Sat Feb 20, 2021 11:48 am

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
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

Bramhachari Khamari
Posts: 69
Joined: Wed Oct 23, 2019 5:52 am

Re: Question related to cohsex gw calculation

Post by Bramhachari Khamari » Sun Feb 21, 2021 11:47 am

Dear Sir,
Thanks a lot for the reply.

Regards,
Bramhachari Khamari
Post Doctoral Fellow
Department of Physics
IIT Kanpur, India.

User avatar
Davide Sangalli
Posts: 376
Joined: Tue May 29, 2012 4:49 pm
Location: Via Salaria Km 29.3, CP 10, 00016, Monterotondo Stazione, Italy
Contact:

Re: Question related to cohsex gw calculation

Post by Davide Sangalli » Mon Feb 22, 2021 12:05 pm

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.
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.oldism.cnr.it/en/davide-sangalli-cv/
http://www.max-centre.eu/

Bramhachari Khamari
Posts: 69
Joined: Wed Oct 23, 2019 5:52 am

Re: Question related to cohsex gw calculation

Post by Bramhachari Khamari » Tue Feb 23, 2021 11:57 am

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,
Bramhachari Khamari
Post Doctoral Fellow
Department of Physics
IIT Kanpur, India.

Post Reply