absorption spectrum

Run-time issues concerning Yambo that are not covered in the above forums.

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absorption spectrum

Postby samaneh » Mon Aug 04, 2014 8:50 pm

Hi
As I know the imaginary part of dielectric function has 3 components
for E||X E||Y E||Z (e.g. in the QE code out put file of epsilon.x)
Would you please explain why there is just one component for E||X and E||Y (E||ab plane)
in yambo code?
Thanks
Best regards
S. Ataei, University of Tehran, Iran
S. Ataei, PhD student at University of Tehran, Iran.
samaneh
 
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Re: absorption spectrum

Postby Daniele Varsano » Mon Aug 04, 2014 9:29 pm

Dear Samaneh,
I'm not sure I have well understood your question.
The dielectric function is a tensor \eps_ij. The absorption then is given by the trace of the tensor in case of isotropic average (e.g. gas phase molecules or in solution),
(eps_xx+eps_yy+eps_zz)/3.
In Yambo the direction of the field is given by (BLongDir or LongDrXd depending of the used approximation), in output you have the diagonal part of the tensor
corresponding then to the absorption along the chosen direction, if you are interested in different direction of the electric field you need to run different calculations corresponding to different LongDir. This is the same that epsilon.x does (according to the manual, as I'm not an expert of that utility), which gives in output the diagonal part of the dielectric matrix (unless off-diagonal component are requested in input), and I imagine it repeats three calculations for three cartesian direction, in independent particle approximation.
Hope it helps,
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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Re: absorption spectrum

Postby samaneh » Tue Aug 05, 2014 6:10 am

Thanks
would you please tell me for longDir 1 0 0 in yambo code
the imaginary part of dielectric function is the same for X and Y direction
is that because of the longDir 1 0 0 or because of the symmetry of the compound??
what is the meaning of the direction of longDir 1 0 0?
does it mean the X direction?
best
S. Ataei, PhD student at University of Tehran, Iran.
samaneh
 
Posts: 165
Joined: Tue Jan 21, 2014 9:03 am

Re: absorption spectrum

Postby Daniele Varsano » Tue Aug 05, 2014 7:41 am

Dear Samaneh,
yes (100) means the x-direction. If it happens that (100) gives the same absorption than y-direction (010), it should be because of symmetries.
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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Re: absorption spectrum

Postby samaneh » Sun Aug 10, 2014 3:56 pm

Hi,
Would you please tell me what is the difference between
BLongDir and LongDrXs?
thanks
S. Ataei, PhD student at University of Tehran, Iran.
samaneh
 
Posts: 165
Joined: Tue Jan 21, 2014 9:03 am

Re: absorption spectrum

Postby Daniele Varsano » Sun Aug 10, 2014 4:35 pm

The first is the direction for the absorption in the bse solution. The latter for the RPA calculation of the static screening.
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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Posts: 1996
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