RPA and alda give the same result?

[zsjan]

Dear all:
The results from yambo -o c -k hartree and yambo -o c -k alda give me the exactly same results about eps file. I have tested the converge but the results are still the same, so what is the possible reason? the input file is below:
for hartree:
optics # [R OPT] Optics
chi # [R CHI] Dyson equation for Chi.
Chimod= "Hartree" # [X] IP/Hartree/ALDA/LRC/BSfxc
NGsBlkXd= 1000 RL # [Xd] Response block size
% QpntsRXd
1 | 1 | # [Xd] Transferred momenta
%
% BndsRnXd
1 | 600 | # [Xd] Polarization function bands
%
% 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
%
and for alda:
optics # [R OPT] Optics
chi # [R CHI] Dyson equation for Chi.
tddft # [R K] Use TDDFT kernel
Chimod= "ALDA" # [X] IP/Hartree/ALDA/LRC/BSfxc
FxcGRLc= 1000 RL # [TDDFT] XC-kernel RL size
NGsBlkXd= 1000 RL # [Xd] Response block size
% QpntsRXd
1 | 1 | # [Xd] Transferred momenta
%
% BndsRnXd
1 | 600 | # [Xd] Polarization function bands
%
% 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
%

[Daniele Varsano]

Dear Shijun,
I do not know on what system you are doing calculations, as no report is attached.
Anyway, if you are dealing with a periodic bulk system, it is reasonable that ALDA gives the same results of RPA, because of the wrong long range limit of the ALDA kernel.
Best,

Daniele

[zsjan]

Dear Shijun,
I do not know on what system you are doing calculations, as no report is attached.
Anyway, if you are dealing with a periodic bulk system, it is reasonable that ALDA gives the same results of RPA, because of the wrong long range limit of the ALDA kernel.
Best,

Daniele

Thank you for your clarification!
I have another question about the parameter BndsRnXd in the calculations. As I vary this parameter from 1|1 to 1|600, the obtained spectrum is always the same. Is it strange? I am expecting that the number of unoccupied bands can influence the spectra very much but this result puzzles me. Why?

[Daniele Varsano]

Dear Shijun,

I have another question about the parameter BndsRnXd in the calculations. As I vary this parameter from 1|1 to 1|600, the obtained spectrum is always the same. Is it strange? I am expecting that the number of unoccupied bands can influence the spectra very much but this result puzzles me. Why?

This is not only strange, but even impossible. Yes it should change until convergence in the energy spectra you are interested in is reached, but at least one unoccupied band has to be included to calculate the response function. The setting:

Code: Select all

%BndsRnXd				
1|1|		#	(Xd)	Polarization function bands
%

does not make any sense. If you upload your input/report/output files we can have a look on what is going on.
Best,
Daniele