GW+BSE calculation for 1D system under an external electric field

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Jing Liu
Posts: 21
Joined: Wed May 06, 2020 8:48 am

GW+BSE calculation for 1D system under an external electric field

Post by Jing Liu » Sat Sep 05, 2020 9:30 am

Dear all,
I have done a GW+BSE calculation for treating a 1D system under an external sawtooth electric field (0.2 V/Å). However, the excitonic peak has even a negative intensity as shown in the attachment.
Could anybody please give me some suggestions? Thank you very much!
Here is my input file.

Code: Select all

rim_cut                        # [R RIM CUT] Coulomb potential
optics                         # [R OPT] Optics
em1s                           # [R Xs] Static Inverse Dielectric Matrix
bss                            # [R BSS] Bethe Salpeter Equation solver
bse                            # [R BSE] Bethe Salpeter Equation.
bsk                            # [R BSK] Bethe Salpeter Equation kernel
em1d                           # [R Xd] Dynamical Inverse Dielectric Matrix
ppa                            # [R Xp] Plasmon Pole Approximation
StdoHash=  40                  # [IO] Live-timing Hashes
Nelectro= 40.00000             # Electrons number
ElecTemp= 0.000000     eV      # Electronic Temperature
BoseTemp= 0.000000     eV      # Bosonic Temperature
OccTresh=0.1000E-4             # Occupation treshold (metallic bands)
NLogCPUs=0                     # [PARALLEL] Live-timing CPU`s (0 for all)
DBsIOoff= "none"               # [IO] Space-separated list of DB with NO I/O. DB=(DIP,X,HF,COLLs,J,GF,CARRIERs,OBS,W,SC,BS,ALL)
DBsFRAGpm= "none"              # [IO] Space-separated list of +DB to FRAG and -DB to NOT FRAG. DB=(DIP,X,W,HF,COLLS,K,BS,QINDX,RT,ELP
FFTGvecs=  82799       RL      # [FFT] Plane-waves
#WFbuffIO                      # [IO] Wave-functions buffered I/O
PAR_def_mode= "memory"       # [PARALLEL] Default distribution mode ("balanced"/"memory"/"workload")
X_all_q_CPU= "1 1 24 2"                # [PARALLEL] CPUs for each role
X_all_q_ROLEs= "q k c v"              # [PARALLEL] CPUs roles (q,g,k,c,v)
X_all_q_nCPU_LinAlg_INV= 4     # [PARALLEL] CPUs for Linear Algebra
BS_CPU= ""                     # [PARALLEL] CPUs for each role
BS_ROLEs= ""                   # [PARALLEL] CPUs roles (k,eh,t)
BS_nCPU_LinAlg_INV= 4          # [PARALLEL] CPUs for Linear Algebra
BS_nCPU_LinAlg_DIAGO= 4        # [PARALLEL] CPUs for Linear Algebra
NonPDirs= "none"               # [X/BSS] Non periodic chartesian directions (X,Y,Z,XY...)
RandQpts= 1000000              # [RIM] Number of random q-points in the BZ
RandGvec= 1            RL      # [RIM] Coulomb interaction RS components
#QpgFull                       # [F RIM] Coulomb interaction: Full matrix
% Em1Anys
 0.00     | 0.00     | 0.00     |        # [RIM] X Y Z Static Inverse dielectric matrix
%
IDEm1Ref=0                     # [RIM] Dielectric matrix reference component 1(x)/2(y)/3(z)
CUTGeo= "box xy"               # [CUT] Coulomb Cutoff geometry: box/cylinder/sphere/ws X/Y/Z/XY..
% CUTBox
 27.00000 | 27.00000 |  0.00000 |        # [CUT] [au] Box sides
%
CUTRadius= 0.000000            # [CUT] [au] Sphere/Cylinder radius
CUTCylLen= 0.000000            # [CUT] [au] Cylinder length
CUTwsGvec= 0.700000            # [CUT] WS cutoff: number of G to be modified
#CUTCol_test                   # [CUT] Perform a cutoff test in R-space
Chimod= "HARTREE"              # [X] IP/Hartree/ALDA/LRC/PF/BSfxc
ChiLinAlgMod= "LIN_SYS"        # [X] inversion/lin_sys
BSEmod= "retarded"             # [BSE] resonant/retarded/coupling
BSKmod= "SEX"                  # [BSE] IP/Hartree/HF/ALDA/SEX
BSSmod= "d"                    # [BSS] (h)aydock/(d)iagonalization/(i)nversion/(t)ddft`
DbGdQsize= 1.000000            # [X,DbGd][o/o] Percentual of the total DbGd transitions to be used
BSENGexx=  20      Ry      # [BSK] Exchange components
#ALLGexx                       # [BSS] Force the use use all RL vectors for the exchange part
BSENGBlk= 3         Ry      # [BSK] Screened interaction block size
#WehDiag                       # [BSK] diagonal (G-space) the eh interaction
#WehCpl                        # [BSK] eh interaction included also in coupling
KfnQPdb= "E < QP_BSE/ndb.QP"                # [EXTQP BSK BSS] Database
KfnQP_N= 1                     # [EXTQP BSK BSS] Interpolation neighbours
% KfnQP_E
 0.000000 | 1.000000 | 1.000000 |        # [EXTQP BSK BSS] E parameters  (c/v) eV|adim|adim
%
KfnQP_Z= ( 1.000000 , 0.000000 )       # [EXTQP BSK BSS] Z factor  (c/v)
KfnQP_Wv_E= 0.000000   eV      # [EXTQP BSK BSS] W Energy reference  (valence)
% KfnQP_Wv
 0.00     | 0.00     | 0.00     |        # [EXTQP BSK BSS] W parameters  (valence) eV| 1|eV^-1
%
KfnQP_Wv_dos= 0.000000 eV      # [EXTQP BSK BSS] W dos pre-factor  (valence)
KfnQP_Wc_E= 0.000000   eV      # [EXTQP BSK BSS] W Energy reference  (conduction)
% KfnQP_Wc
 0.00     | 0.00     | 0.00     |        # [EXTQP BSK BSS] W parameters  (conduction) eV| 1 |eV^-1
%
KfnQP_Wc_dos= 0.000000 eV      # [EXTQP BSK BSS] W dos pre-factor  (conduction)
DipApproach= "G-space v"       # [Xd] [G-space v/R-space x/Covariant/Shifted grids]
#DipPDirect                    # [Xd] Directly compute <v> also when using other approaches for dipoles
ShiftedPaths= ""               # [Xd] Shifted grids paths (separated by a space)
Gauge= "length"                # [BSE] Gauge (length|velocity)
#NoCondSumRule                 # [BSE] Do not impose the conductivity sum rule in velocity gauge
#MetDamp                       # [BSE] Define \w+=sqrt(\w*(\w+i\eta))
DrudeWBS= ( 0.00     , 0.00     )  eV  # [BSE] Drude plasmon
#Reflectivity                  # [BSS] Compute reflectivity at normal incidence
BoseCut=  0.10000              # [BOSE] Finite T Bose function cutoff
% BEnRange
  0.00000 | 5.00000 | eV      # [BSS] Energy range
%
% BDmRange
  0.10000 |  0.10000 | eV      # [BSS] Damping range
%
BEnSteps= 600                  # [BSS] Energy steps
% BLongDir
 1.000000 | 0.000000 | 0.000000 |        # [BSS] [cc] Electric Field
%
% BSEBands
   19 | 24 |                   # [BSK] Bands range
%
% BSEEhEny
-1.000000 |-1.000000 | eV      # [BSK] Electron-hole energy range
%
WRbsWF                        # [BSS] Write to disk excitonic the WFs
#BSSPertWidth                  # [BSS] Include QPs lifetime in a perturbative way
XfnQPdb= "E < QP_BSE/ndb.QP"                # [EXTQP Xd] Database
XfnQP_N= 1                     # [EXTQP Xd] Interpolation neighbours
% XfnQP_E
 0.000000 | 1.000000 | 1.000000 |        # [EXTQP Xd] E parameters  (c/v) eV|adim|adim
%
XfnQP_Z= ( 1.000000 , 0.000000 )       # [EXTQP Xd] Z factor  (c/v)
XfnQP_Wv_E= 0.000000   eV      # [EXTQP Xd] W Energy reference  (valence)
% XfnQP_Wv
 0.00     | 0.00     | 0.00     |        # [EXTQP Xd] W parameters  (valence) eV| 1|eV^-1
%
XfnQP_Wv_dos= 0.000000 eV      # [EXTQP Xd] W dos pre-factor  (valence)
XfnQP_Wc_E= 0.000000   eV      # [EXTQP Xd] W Energy reference  (conduction)
% XfnQP_Wc
 0.00     | 0.00     | 0.00     |        # [EXTQP Xd] W parameters  (conduction) eV| 1 |eV^-1
%
XfnQP_Wc_dos= 0.000000 eV      # [EXTQP Xd] W dos pre-factor  (conduction)
% QpntsRXs
  1 | 10 |                     # [Xs] Transferred momenta
%
% BndsRnXs
   1 | 144 |                   # [Xs] Polarization function bands
%
NGsBlkXs= 7            Ry      # [Xs] Response block size
GrFnTpXs= "T"                  # [Xs] Green`s function (T)ordered,(R)etarded,(r)senant,(a)ntiresonant [T, R, r, Ta, Ra]
% DmRngeXs
  0.10000 |  0.10000 | eV      # [Xs] Damping range
%
CGrdSpXs= 100.0000             # [Xs] [o/o] Coarse grid controller
% EhEngyXs
-1.000000 |-1.000000 | eV      # [Xs] Electron-hole energy range
%
% LongDrXs
 1.000000 | 0.000000 | 0.000000 |        # [Xs] [cc] Electric Field
%
DrudeWXs= ( 0.00     , 0.00     )  eV  # [Xs] Drude plasmon
XTermKind= "none"              # [X] X terminator ("none","BG" Bruneval-Gonze)
XTermEn= 40.00000      eV      # [X] X terminator energy (only for kind="BG")
% QpntsRXp
  1 | 10 |                     # [Xp] Transferred momenta
%
% BndsRnXp
   1 | 144 |                   # [Xp] Polarization function bands
%
NGsBlkXp= 7         Ry      # [Xp] Response block size
CGrdSpXp= 100.0000             # [Xp] [o/o] Coarse grid controller
% EhEngyXp
-1.000000 |-1.000000 | eV      # [Xp] Electron-hole energy range
%
% LongDrXp
1.000 | 0.000    | 0.000    |        # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138     eV      # [Xp] PPA imaginary energy
Jing Liu
PhD student
Beijing Institute of Technology, China

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claudio
Posts: 448
Joined: Tue Mar 31, 2009 11:33 pm
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Re: GW+BSE calculation for 1D system under an external electric field

Post by claudio » Sat Sep 05, 2020 5:04 pm

Dear Jing Liu

is your system metallic? does it have a gap?
What's happen when the external field is zero?

A small error in your input, you should not use quasi-particle
in the calculation of the epsilon, remove the line

XfnQPdb= "E < QP_BSE/ndb.QP" # [EXTQP Xd] Database

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

Jing Liu
Posts: 21
Joined: Wed May 06, 2020 8:48 am

Re: GW+BSE calculation for 1D system under an external electric field

Post by Jing Liu » Sun Sep 06, 2020 4:29 am

Dear Claudio,
Many thanks for your kind suggestion.
My system is semiconductive and everything goes well when the external field is zero and even at 0.1 V/Å. I have to do the BSE calculation that reading the QP corrections from a previous GW calculation in order to compare my results with VASP. In this case, what should I do ? :cry:
I am so sorry that I failed to upload the optical absorption spectra at 0.2 V/Å before and I have uploaded it again.
Thank you!
Best,
Jing Liu
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Jing Liu
PhD student
Beijing Institute of Technology, China

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Daniele Varsano
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Re: GW+BSE calculation for 1D system under an external electric field

Post by Daniele Varsano » Mon Sep 07, 2020 7:38 am

Dear Jing Liu,
please sign your posts with your name and affiliation, this is a rule of the forum and you can do once for all by filling the signature in your user profile.

The variable to include GW QP corrections in the BSE is

Code: Select all

KfnQPdb
and not

Code: Select all

XfnQPdb
as in this way you are including it in the screening and this is not consistent.

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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claudio
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Re: GW+BSE calculation for 1D system under an external electric field

Post by claudio » Mon Sep 07, 2020 8:30 am

Dear Jing Liu

I do not have a solution to your problem, anyway hereafter some suggestions and questions:

1) Try to use the full BSE
BSEmod= "coupling"
WehCpl

2) plot the column 4 of your BSE output file,
it gives you the GW+IP spectra, and check if it is good

3) are you using a sufficiently large supercell?
and is the electric field well well-positioned?

4) put in the forum the spectra for electric field 0.1 if you have it

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

Jing Liu
Posts: 21
Joined: Wed May 06, 2020 8:48 am

Re: GW+BSE calculation for 1D system under an external electric field

Post by Jing Liu » Thu Sep 10, 2020 2:12 pm

Dear Claudio,
Thanks for your suggestions!
1) I tried the full BSE method and the result is the same as before.
2) The GW+IP spectra is as follows
GW+IP.tif
3) The nanowire is along c direction and the unit cell I chose is 15*15*c Å^3, I think it's large enough. The elecgric field was applied by using QE package and here is the related input fiel.
&CONTROL
tefield = .true.
dipfield = .true.
&SYSTEM
emaxpos = 0.987
eopreg = 0.1
edir = 1
eamp = 0.0039
4) Here is the spectra for electric field 0.1
0.1.tif
Best,
Jing Liu
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Jing Liu
PhD student
Beijing Institute of Technology, China

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claudio
Posts: 448
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Re: GW+BSE calculation for 1D system under an external electric field

Post by claudio » Mon Sep 14, 2020 10:44 am

Dear Jing Liu
I do not see anythings strange in your images and inputs, please put also
all the report files, a log file and the GW input, and the QE inputs

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

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