Hi
As I know the imaginary part of dielectric function has 3 components
for EX EY EZ (e.g. in the QE code out put file of epsilon.x)
Would you please explain why there is just one component for EX and EY (Eab plane)
in yambo code?
Thanks
Best regards
S. Ataei, University of Tehran, Iran
absorption spectrum
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 Posts: 165
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absorption spectrum
S. Ataei, PhD student at University of Tehran, Iran.
 Daniele Varsano
 Posts: 2322
 Joined: Tue Mar 17, 2009 2:23 pm
 Contact:
Re: absorption spectrum
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 offdiagonal 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
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 offdiagonal 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
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/

 Posts: 165
 Joined: Tue Jan 21, 2014 9:03 am
Re: absorption spectrum
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
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.
 Daniele Varsano
 Posts: 2322
 Joined: Tue Mar 17, 2009 2:23 pm
 Contact:
Re: absorption spectrum
Dear Samaneh,
yes (100) means the xdirection. If it happens that (100) gives the same absorption than ydirection (010), it should be because of symmetries.
Best,
Daniele
yes (100) means the xdirection. If it happens that (100) gives the same absorption than ydirection (010), it should be because of symmetries.
Best,
Daniele
Dr. Daniele Varsano
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/

 Posts: 165
 Joined: Tue Jan 21, 2014 9:03 am
Re: absorption spectrum
Hi,
Would you please tell me what is the difference between
BLongDir and LongDrXs?
thanks
Would you please tell me what is the difference between
BLongDir and LongDrXs?
thanks
S. Ataei, PhD student at University of Tehran, Iran.
 Daniele Varsano
 Posts: 2322
 Joined: Tue Mar 17, 2009 2:23 pm
 Contact:
Re: absorption spectrum
The first is the direction for the absorption in the bse solution. The latter for the RPA calculation of the static screening.
Best
Daniele
Best
Daniele
Dr. Daniele Varsano
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/