ElecTemp in RPA dielectric function

Deals with issues related to computation of optical spectra, in RPA (-o c) or by solving the Bethe-Salpeter equation (-o b). Includes local field effects, excitons, etc.

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ElecTemp in RPA dielectric function

Postby Weiqing Zhou » Tue Feb 19, 2019 1:58 pm

Hi all,

I calculated optical response of a metal material and use RPA with local field effect to obtain dielectric function. I find the result would change a lot if I set different ElecTemp. I don't understand why the imaginary static dielectric function ( imaginary dielectric function at /Omega=0 ) is not zero when I set ElecTemp = 0.0 eV.
You can check the output with 0K and 300K in attachment.

Best,
Weiqing
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Weiqing Zhou
Phd student
Wuhan University
Wuhan, Hubei, 430072
Weiqing Zhou
 
Posts: 43
Joined: Thu Sep 06, 2018 7:57 am
Location: Wuhan University

Re: ElecTemp in RPA dielectric function

Postby Daniele Varsano » Wed Feb 20, 2019 9:53 am

Dear Wiking,

this is probably becuase your temperature it is not exactly zero.
From the report you can see:
Code: Select all
[X]Electronic Temp. [ev K]: 0.8617E-5 0.1000

and this happens as the system is metallic.
Anyway the values you get at omega=0 it is also affected by the smearing you used:
Code: Select all
 % DmRngeXd
 |   0.10000 |  0.10000 | eV      # [Xd] Damping range
 | %

you can think to low that value.

Note also that, to have a correct description of the metallic behavior it would be appropriate to add the Drude term in your response function:
Code: Select all
 [WARNING] The system is a metal but Drude term not included.


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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Daniele Varsano
 
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Re: ElecTemp in RPA dielectric function

Postby Weiqing Zhou » Wed Mar 13, 2019 1:37 pm

Dear Daniele,

Thanks for you kind reply!

I add Drude term into dielectric function (by DrudeWXd). For q1 (0,0,0), I find that there appears a very large value around /omega=0 in dielectric function. But for finite q, Drude term makes no difference in dielectric function. Is it right?

Best,
Weiqing
Weiqing Zhou
Phd student
Wuhan University
Wuhan, Hubei, 430072
Weiqing Zhou
 
Posts: 43
Joined: Thu Sep 06, 2018 7:57 am
Location: Wuhan University

Re: ElecTemp in RPA dielectric function

Postby Daniele Varsano » Wed Mar 13, 2019 1:41 pm

Dear Weiqing,
indeed, the Drude term takes into account the term coming for interband transitions in the limit q->0.
For finite q, interband transitions are correctly taken into account in the response function

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/
User avatar
Daniele Varsano
 
Posts: 1950
Joined: Tue Mar 17, 2009 2:23 pm


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