Momentum dependent Independent-particle-approximation

Deals with issues related to computation of optical spectra in reciprocal space: RPA, TDDFT, local field effects.

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Fadil
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Joined: Sun May 24, 2020 1:56 pm

Momentum dependent Independent-particle-approximation

Post by Fadil » Wed Jul 21, 2021 7:46 pm

Dear all,

I am calculating q-dependent dielectric function for a metallic system.
But I realized that the program does not calculate all the q-points I gave as input and after calculating some q points it stopped without error. (r-IP_optics_chi_dipoles_q34)

I encountered another problem when I was changing the electric field direction with 'LongDrXd' to calculate the dielectric function in different directions.
Except for q1, even if I set the electric field direction in different directions, it calculates the same dielectric function.(see the epsilon files in the attachment)

Best
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Dr. Fadıl İYİKANAT
ICFO-The Institute of Photonic Sciences
Barcelona-SPAIN

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Daniele Varsano
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Re: Momentum dependent Independent-particle-approximation

Post by Daniele Varsano » Thu Jul 22, 2021 6:41 am

Dear Fadil,
I encountered another problem when I was changing the electric field direction with 'LongDrXd' to calculate the dielectric function in different directions.
Except for q1, even if I set the electric field direction in different directions, it calculates the same dielectric function.(see the epsilon files in the attachment)
This is correct, the 'LongDrXd' set the direction in the q->0 limit and it is meaningful for iq=1. For the other q the direction is given by the finite momentum of the selected q point.
after calculating some q points it stopped without error.
This should be investigated, anyway before trying to spot the problem, let me ask you to update to a more recent versione of the code as many improvements and change happened in the newer releases:

Code: Select all

git clone git@github.com:yambo-code/yambo.git yambo
If the problem persists post here again providing the report again, input file and eventually any useful info (error message if any) in one of the log files.

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/

Fadil
Posts: 56
Joined: Sun May 24, 2020 1:56 pm

Re: Momentum dependent Independent-particle-approximation

Post by Fadil » Sun Jul 25, 2021 4:09 pm

Dear Daniele,

Thank you for the response.
This is correct, the 'LongDrXd' set the direction in the q->0 limit and it is meaningful for iq=1. For the other q the direction is given by the finite momentum of the selected q point.
So, since a two-dimensional material is not periodic in the z direction (no q in the z direction), how can we calculate \eps_{z}?
Dr. Fadıl İYİKANAT
ICFO-The Institute of Photonic Sciences
Barcelona-SPAIN

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Daniele Varsano
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Re: Momentum dependent Independent-particle-approximation

Post by Daniele Varsano » Sun Jul 25, 2021 5:51 pm

Dear Fadil,

you can calculate the lim q-->0 in the z direction using LongDrXd=0,0,1
you cannot calculate the dispersion wrt q, but this is not very meaningful as a 2D system has not dispersion in that direction (flat bands).

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/

Fadil
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Re: Momentum dependent Independent-particle-approximation

Post by Fadil » Sun Jul 25, 2021 7:53 pm

Thank you!

Best
Dr. Fadıl İYİKANAT
ICFO-The Institute of Photonic Sciences
Barcelona-SPAIN

Fadil
Posts: 56
Joined: Sun May 24, 2020 1:56 pm

Re: Momentum dependent Independent-particle-approximation

Post by Fadil » Fri Aug 20, 2021 11:31 am

Dear all

Is it possible to define kpoint mesh externally and calculate the momentum dependent GW-BSE spectrums?
When I define the kpoint mesh irregularly, it does not recognize my kpoint mesh and it is not possible to generate the input files with created SAVE files.

Best
Dr. Fadıl İYİKANAT
ICFO-The Institute of Photonic Sciences
Barcelona-SPAIN

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Davide Sangalli
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Re: Momentum dependent Independent-particle-approximation

Post by Davide Sangalli » Tue Aug 31, 2021 12:49 pm

Dear Fadil,
yambo can compute finite-q optical properties selecting the q-points q=k-k' where both k and k' belong to a regular grid.
It is not possible to use random grids or any other grid.

Best,
D.
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
https://sites.google.com/view/davidesangalli
http://www.max-centre.eu/

Fadil
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Re: Momentum dependent Independent-particle-approximation

Post by Fadil » Fri Sep 03, 2021 12:37 pm

I see.
Thank you!
Dr. Fadıl İYİKANAT
ICFO-The Institute of Photonic Sciences
Barcelona-SPAIN

Fadil
Posts: 56
Joined: Sun May 24, 2020 1:56 pm

Re: Momentum dependent Independent-particle-approximation

Post by Fadil » Thu Sep 22, 2022 5:36 pm

Dear all,

From previous posts I know for iq=1, in the IPA, using the 'LongDrXd' we can extract the dielectric tensor components (bulk material) along the xx, yy, zz-directions.
Is it possible to obtain dielectric tensor components for the finite-q calculations (iq/=1)?
What I mean is that can we extract z-component of dielectric function in a specific point like K-point (for q in the plane) in the Brillouin Zone?

Best
Dr. Fadıl İYİKANAT
ICFO-The Institute of Photonic Sciences
Barcelona-SPAIN

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Daniele Varsano
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Re: Momentum dependent Independent-particle-approximation

Post by Daniele Varsano » Mon Sep 26, 2022 3:19 pm

Dear Fadil,
when looking at finite q, you are simulating an eels spectrum, so the perturbation is longitudinal in the direction of the incoming electron.

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/

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