Yambo Community Forum

Hello,
I try to calculate dielectric functions with RPA. When I try to vary the variable GrFnTPXd (c,t, a,r) I have in the output always a 'c' (not a 't' as it is said to be the default input).
Is the RPA-calculation just implemented with the c-Greensfunction or why does this happen?

Thanks and Regards

Stephan

Dear Stephan,
I think that now the default is the causal one. I need to check why it is not working if you change the default.

Best,
Daniele

Hi Daniele,
thank you for your reply.
My Input file looks like this:
#
# ::: ::: ::: :::: :::: ::::::::: ::::::::
# :+: :+: :+: :+: +:+:+: :+:+:+ :+: :+: :+: :+:
# +:+ +:+ +:+ +:+ +:+ +:+:+ +:+ +:+ +:+ +:+ +:+
# +#++: +#++:++#++: +#+ +:+ +#+ +#++:++#+ +#+ +:+
# +#+ +#+ +#+ +#+ +#+ +#+ +#+ +#+ +#+
# #+# #+# #+# #+# #+# #+# #+# #+# #+#
# ### ### ### ### ### ######### ########
#
# GPL Version 3.4.1 Revision 3187
# http://www.yambo-code.org
#
optics # [R OPT] Optics
chi # [R CHI] Dyson equation for Chi.
Chimod= "Hartree" # [X] IP/Hartree/ALDA/LRC/BSfxc
NGsBlkXd=400
FFTGvecs= 750
% QpntsRXd
1 | 1 | # [Xd] Transferred momenta
%
% BndsRnXd
14 | 42 | # [Xd] Polarization function bands
%
GrFnTpXd="a" # [Xd] Green`s function t/c/r/a
% EnRngeXd
0.00000 | 10.00000 | eV # [Xd] Energy range
%
% DmRngeXd
0.10000 | 0.10000 | eV # [Xd] Damping range
%
ETStpsXd= 100 # [Xd] Total Energy steps
% LongDrXd 1.000000 | 0.000000 | 0.000000 | # [Xd] [cc] Electric Field
%
DrudeWXd=(2.541677 , 0.3719527 ) eV
%

In the output I receive
#
# YAMBO@QuanCal x 004 CPUs * 06/25/2015 10:23 [start]
# 06/25/2015 10:38 [end]
#
# Cpu Timing [Min/Max/Average]: 11m-18s/11m-19s/11m-19s
#
# .-Input file : yambo.in
# | optics # [R OPT] Optics
# | chi # [R CHI] Dyson equation for Chi.
# | FFTGvecs= 755 RL # [FFT] Plane-waves
# | Chimod= "Hartree" # [X] IP/Hartree/ALDA/LRC/BSfxc
# | NGsBlkXd= 401 RL # [Xd] Response block size
# | % QpntsRXd
# | 1 | 1 | # [Xd] Transferred momenta
# | %
# | % BndsRnXd
# | 14 | 42 | # [Xd] Polarization function bands
# | %
# | GrFnTpXd= "c" # [Xd] Green`s function t/c/r/a
# | % EnRngeXd
# | 0.00000 | 10.00000 | eV # [Xd] Energy range
# | %
# | % DmRngeXd
# | 0.10000 | 0.10000 | eV # [Xd] Damping range
# | %
# | ETStpsXd= 100 # [Xd] Total Energy steps
# | DrudeWXd= ( 2.541677 , 0.371953 ) eV # [Xd] Drude plasmon
# | % LongDrXd
# | 0.1000E-4 | 0.000 | 0.000 | # [Xd] [cc] Electric Field
# | %

Might this happen because the Green's Function isn't used at all?

Thanks and Regards

Stephan

Dear Stephan,
The flag indicate if the response function is causal, resonant etc..
it looks that the code for some reason force the response function to be causal.
Do you have a finite electronic temperature? You can check it in the report file.

Best,
Daniele

Hello Daniele,
indeed I have a finite electronic temperature:
...
[RD./SAVE//db.dipoles]--------------------------------------
Brillouin Zone Q/K grids (IBZ/BZ): 288 3375 288 3375
*WRN* RL vectors (WF): 48211
Electronic Temperature [K]: 300.00000
Bosonic Temperature [K]: 300.00000
...

How is this concerned with the Greensfunction I choose?

Thanks and Regards
Stephan

Dear Stephan,
when temperature is finite only causal response function make sense.
If you want, you can set your temperature to zero by setting ElecTemp=0 in your input file, and Yambo will recalculate the occupation numbers accordingly.
Anyway why do you want response function other than causal, which is the one having physical sense?. The other options are there more or less for testing
purpose.
Best,

Daniele

Hi Daniele,
thank you for your reply. I ask these questions because I want to receive an understanding as deep as possible.
I'm a Master student and I'm working at a Institute for experimental physics, so I'm the only one in my institute who is concerned with simulations.
I hope my questions are not so stupid..

Thankks and regards

Stephan

Dear Stephan,

. I ask these questions because I want to receive an understanding as deep as possible.

Good attitude

I hope my questions are not so stupid..

Not, they are not at all, and feel free to post any question related to the code.
Best,
Daniele