Yambo Community Forum

Dear Yambo developers:
I would like to perform some TDHF calculations for small molecules.
This requires to use bare Coulomb to replace the screened Coulomb kernel
in the BSE part. Is there an option in Yambo to perform such calculations, either
by keywords or slight modification of the source code?

Best regards,
Deyu Lu


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Deyu Lu (Ph.D)

190 Chemistry Building
University of California, Davis
One Shields Avenue
Davis, CA 95616
Office phone: (530) 754-9663
Group Webpage: http://angstrom.ucdavis.edu/

***************************************************************************

Dear Deyu Lu,
yes, in line of principle you can do it, but
unfortunately this option it is not in the gpl version.
Anyway the easiest way to do it is to replace the dielectric matrix,
in the construction of the direct part of the kernel
with a delta function in /bse/K.F subroutine.
Anyway let me warn you that in GPL version the
Bethe Salpeter equation is implemented only considering
the resonant part (Tamm-Dankof approximation) and for
small isolated molecules that could be not a good approximation:
see i.e. :
Exciton-plasmon states in nanoscale materials: breakdown of the Tamm-Dancoff approximation
M. Grüning, A. Marini and X. Gonze
Nano Letters, 9, 2820 (2009)

Hope it helps,

Daniele

deyulu wrote:Dear Yambo developers:
I would like to perform some TDHF calculations for small molecules.
This requires to use bare Coulomb to replace the screened Coulomb kernel
in the BSE part. Is there an option in Yambo to perform such calculations, either
by keywords or slight modification of the source code?

Dear Deyu Lu,

Daniele is right, as the TDHF part is not in the GPL part. However it is such a small part of the code that I could think of releasing in the GPL source. If you are interested I can do it in the next days by including the change only in the SVN repository.

Daniele, thank you for the information.
Andrea, if you can release the tdhf feature in the GPL source, it would be great.
Thank you for the help.


***************************************************************************
Deyu Lu (Ph.D)

190 Chemistry Building
University of California, Davis
One Shields Avenue
Davis, CA 95616
Office phone: (530) 754-9663
Group Webpage: http://angstrom.ucdavis.edu/

***************************************************************************

Time-Dependent Hartree Fock has been added to the latest revision in the SVN repository. Check here for more informations.

Dear Andrea:
Thank you for putting tdhf in the svn. As I'm testing version 4.8.5,
there are some errors in the report file, e.g. " *ERR* |Correlation [res]:no"
and "|W interaction is bare :no". I guess that my input file is incorrect.
Enclosed is my input and part of the report file that concerns the bse solver.
Could you tell me where the problem is?

Best
Deyu Lu

***************************************************************************
Deyu Lu (Ph.D)

190 Chemistry Building
University of California, Davis
One Shields Avenue
Davis, CA 95616
Office phone: (530) 754-9663
Group Webpage: http://angstrom.ucdavis.edu/

***************************************************************************

------------------------------------------input-------------------------------------
optics # [R OPT] Optics
bse # [R BSK] Bethe Salpeter Equation.
tdhf # [TDHF]
bss # [R BSS] Bethe Salpeter Equation solver
BSresKmod= "xc" # [BSK] Resonant Kernel mode. (`x`;`c`;`d`)
% BSEBands
1 | 8 | # [BSK] Bands range
%
FFTGvecs= 23583 RL # (FFT) Plane-waves
BSENGexx= 23583 RL # [BSK] Exchange components
BSENGBlk= 23583 RL # [BSK] Screened interaction block size
BSSmod= "d" # [BSS] Solvers `h/d/i/t`
% BEnRange
0.00000 | 15.00000 | eV # [BSS] Energy range
%
% BDmRange
0.0010000 | 0.0010000 | eV # [BSS] Damping range
%
BEnSteps= 100 # [BSS] Energy steps
% BLongDir
1.000000 | 0.000000 | 0.000000 | # [BSS] [cc] Electric Field
%
BSHayTrs= -0.00200

-------------------------------------output-----------------------------------
[04] Bethe-Salpeter Kernel
==========================

[RD./SAVE//db.BS_Q1]----------------------------------------
Brillouin Zone Q/K grids (IBZ/BZ): 1 1 1 1
RL vectors (WF): 23583
BS kernel wavefunctions :Perdew & Zunger (xc)
Static diel. fun. energies :Perdew & Zunger (xc)
wavefunctions :Perdew & Zunger (xc)
BSK|Identifier : 8490
|Dimension : 16
|Bands : 1 8
|Exchange [res]:yes
*ERR* |Correlation [res]:no
|Kernel`s coupling :no
|Exchange [cpl]:no
|W interaction is bare :no
|Correlation [cpl]:no
*ERR* |ALDA kernel in R-space :yes
|RL vectors [exchange]: 23583
|E/h energy range [ev]:-1.000000 -1.000000
|Coupling range [o/o]: 100.0000 100.0000
- S/N 002955 ---------------------------- v.03.02.01 r.485 -
[BSE] Kernel dimension : 16
[BSE] Exchange components : 23583

[04.01] Screneed interaction header I/O
=======================================


[WARNING]BS section skipped. PP/Em1s DB does not fit/exist