Multiplied Linear response?

Deals with issues related to computation of optical spectra, in RPA (-o c) or by solving the Bethe-Salpeter equation (-o b). Includes local field effects, excitons, etc.

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Yadong Wei
Posts: 8
Joined: Fri Jun 08, 2018 3:50 am
Location: Harbin,China PR

Multiplied Linear response?

Post by Yadong Wei » Thu Jun 13, 2019 3:45 am

Dear Sir:
The problem I recently ran into is quite simple.
I used the same database generated by QE(i.e. .save folder), the same yambo_BSE.in configurations, but different versions: yambo-4.2.2 and yambo-4.3.2.
The result in 'o-2D_WR_WC.eps_q1_diago_bse' is different in magnitude, but the shape are very close to each other. The ratio is approximately 1.165 x 10 ^ (7).
Is there some changes related to this, between these two versions ?
Thanks a lot
yambo_BSE.in is here

Code: Select all

#                                                           
#  /$$     /$$ /$$$$$$  /$$      /$$ /$$$$$$$   /$$$$$$     
# |  $$   /$$//$$__  $$| $$$    /$$$| $$__  $$ /$$__  $$    
#  \  $$ /$$/| $$  \ $$| $$$$  /$$$$| $$  \ $$| $$  \ $$    
#   \  $$$$/ | $$$$$$$$| $$ $$/$$ $$| $$$$$$$ | $$  | $$    
#    \  $$/  | $$__  $$| $$  $$$| $$| $$__  $$| $$  | $$    
#     | $$   | $$  | $$| $$\  $ | $$| $$  \ $$| $$  | $$    
#     | $$   | $$  | $$| $$ \/  | $$| $$$$$$$/|  $$$$$$/    
#     |__/   |__/  |__/|__/     |__/|_______/  \______/     
#                                                           
# GPL Version 4.3.2 Revision 134. (Based on r.15658 h.afdb12
#                       MPI Build                           
#               http://www.yambo-code.org                   
#
rim_cut                        # [R RIM CUT] Coulomb potential
optics                         # [R OPT] Optics
ppa                            # [R Xp] Plasmon Pole Approximation
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
StdoHash=  40                  # [IO] Live-timing Hashes
Nelectro= 18.00000             # Electrons number
ElecTemp=  0.02585     eV      # Electronic Temperature
BoseTemp=-1.000000     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,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
MEM_tresh=  53590      Kb      # [MEMORY] Treshold on traced memory allocations/deallocations
#WFbuffIO                      # [IO] Wave-functions buffered I/O
PAR_def_mode= "balanced"       # [PARALLEL] Default distribution mode ("balanced"/"memory"/"workload")
X_all_q_CPU= "30 1 1 1 1"                # [PARALLEL] CPUs for each role
X_all_q_ROLEs= "q g k c v"              # [PARALLEL] CPUs roles (q,g,k,c,v)
X_all_q_nCPU_LinAlg_INV= 1     # [PARALLEL] CPUs for Linear Algebra
BS_CPU= "30 1 1"                     # [PARALLEL] CPUs for each role
BS_ROLEs= "k eh t"                   # [PARALLEL] CPUs roles (k,eh,t)
BS_nCPU_LinAlg_INV= 1          # [PARALLEL] CPUs for Linear Algebra
BS_nCPU_LinAlg_DIAGO= 1        # [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= 107          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 z"                # [CUT] Coulomb Cutoff geometry: box/cylinder/sphere/ws X/Y/Z/XY..
% CUTBox
  0.00000 |  0.00000 | 32.00000 |        # [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= 5            Ry      # [BSK] Screened interaction block size
#WehDiag                       # [BSK] diagonal (G-space) the eh interaction
#WehCpl                        # [BSK] eh interaction included also in coupling
KfnQPdb= "none"                # [EXTQP BSK BSS] Database
KfnQP_N= 1                     # [EXTQP BSK BSS] Interpolation neighbours
% KfnQP_E
 2.141215 | 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 | 10.00000 | eV      # [BSS] Energy range
%
% BDmRange
  0.10000 |  0.10000 | eV      # [BSS] Damping range
%
BEnSteps=1001                  # [BSS] Energy steps
% BLongDir
 1.000000 | 0.000000 | 0.000000 |        # [BSS] [cc] Electric Field
%
% BSEBands
  5 | 11 |                     # [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= "none"                # [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)
% QpntsRXp
  1 | 30 |                     # [Xp] Transferred momenta
%
% BndsRnXp
  1 | 25 |                     # [Xp] Polarization function bands
%
NGsBlkXp= 6            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
 1.000000 | 0.000000 | 0.000000 |        # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138     eV      # [Xp] PPA imaginary energy
XTermKind= "none"              # [X] X terminator ("none","BG" Bruneval-Gonze)
XTermEn= 40.00000      eV      # [X] X terminator energy (only for kind="BG")
Yadong Wei
weiyd@hit.edu.cn
School of Physics
Harbin Institute of Technology,150001

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Daniele Varsano
Posts: 2660
Joined: Tue Mar 17, 2009 2:23 pm
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Re: Multiplied Linear response?

Post by Daniele Varsano » Wed Jun 19, 2019 9:21 am

Dear Yadong Wei,
yes, as you have observed we have changed the way to compute q->0 limit only when using a cutoff coulomb potential, so 2D/1D/0D structure.
In this case the epsilon it is not well defined and we think this is the correct way to proceed in order to have consistencies. The interpretation of such small numbers is that considering your system as 3D it is essentially vacuum. Note that it is just a constant so you can multiply by a factor in order to recover the previous result. We will change this anyway soon in order to relate the spectrum to the experimental observables, in the meantime you can just multiply it for a factor (considering that absorption is given in arbitrary units).

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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