BSE

[zchen]

Hi, all
I try to calculae the BSE for the bilayer graphene. I got the error message, BS section skipped PP/Emis DB does not fit/exit.
I used command yambo -b -o b -y h.

Zhifan Chen
Dept. of Physics
Clark Atlanta University
USA

[andrea marini]

Dear Zhifan Chen, please post

• Input file
• report file and standard output ( you can create it by running "yambo >&/dev/null ")
• The list of files in your SAVE folder

without these informations it is hard to say where the problem is.

[zchen]

Dr. marini:
Thank you very much. Here is the list of files in SAVE directory:
db.em1s, db.gops, db.HF_and_locXC, db.kindx, db.ostnts, db.pp, s.db1, s.kb_pp, s.wf

Following is the input file

optics # [R OPT] Optics
bse # [R BSK] Bethe Salpeter Equation.
bss # [R BSS] Bethe Salpeter Equation solver
BSresKmod= "xc" # [BSK] Resonant Kernel mode. (`x`;`c`;`d`)
% BSEBands
1 | 100 | # [BSK] Bands range
%
BSENGBlk= 1 RL # [BSK] Screened interaction block size
BSENGexx= 25113 RL # [BSK] Exchange components
BSSmod= "d" # [BSS] Solvers `h/d/i/t`
% BEnRange
1.00000 | 4.00000 | eV # [BSS] Energy range
%
% BDmRange
0.10000 | 0.10000 | eV # [BSS] Damping range
%
BEnSteps= 40 # [BSS] Energy steps
% BLongDir
1.000000 | 0.000000 | 0.000000 | # [BSS] [cc] Electric Field

Following is the report file

[01] Files & I/O Directories
============================

CORE databases in .
Additional I/O in .
Communications in .
Input file is yambo.in
Report file is ./r_optics_bse_bss

[RD./SAVE//s.db1]-------------------------------------------
Bands : 100
K-points : 18
G-vectors [RL space]: 27168
Components [wavefunctions]: 27168
Symmetries [spatial+T-rev]: 2
Spinor components : 1
Spin polarizations : 1
Temperature [ev]: 0.000000
Electrons : 112.0000
WF G-vectors : 27168
Max atoms/species : 28
No. of atom species : 1
- S/N 001132 ---------------------------- v.03.02.01 r.448 -

[02] CORE Variables Setup
=========================

[02.01] Unit cells
==================

Unit cell is HCP

... containing 28C atoms

... with scaling factors [a.u.]: 12.28020 10.63496 34.50489

Direct Lattice(DL) unit cell [iru]
A1 = 1.000000 0.000000 0.000000
A2 =-0.500000 1.000000 0.000000
A3 = 0.000000 0.000000 1.000000

DL volume [au]: 4506.

Reciprocal Lattice(RL) unit cell [iku]
B1 = 1.000000 0.500000 0.000000
B2 = 0.000000 1.000000 0.000000
B3 = 0.000000 0.000000 1.000000[02.02] Symmetries
==================

DL (S)ymmetries [cc]
[S1] 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000

[SYMs] Time-reversal derived K-space symmetries: 2 2
[SYMs] Spatial inversion 2 is NOT a symmetry
[SYMs] Group table built correctly

[02.03] RL shells
=================

Shells, format: [S#] G_RL(mHa)

[S1301]:25113( 6901.) [S1300]:25089( 6901.) [S1299]:25041( 6898.) [S1298]:25017( 6897.)
[S1297]:24993( 6896.) [S1296]:24969( 6893.) [S1295]:24945( 6883.) [S1294]:24933( 6880.)
[S1293]:24909( 6877.) [S1292]:24885( 6877.) [S1291]:24861( 6876.) [S1290]:24849( 6874.)
[S1289]:24801( 6874.) [S1288]:24777( 6874.) [S1287]:24753( 6873.) [S1286]:24729( 6867.)
[S1285]:24717( 6867.) [S1284]:24693( 6865.) [S1283]:24669( 6862.) [S1282]:24645( 6860.)
[S1281]:24633( 6857.) [S1280]:24609( 6856.) [S1279]:24597( 6852.) [S1278]:24549( 6852.)
[S1277]:24513( 6851.) [S1276]:24489( 6849.) [S1275]:24477( 6847.) [S1274]:24465( 6847.)
[S12]:71( 1023.) [S11]:65( 937.8650) [S10]:53( 910.4777) [S9]:51( 804.6609)
[S8]:39( 728.3821) [S7]:37( 694.0355) [S6]:25( 618.2305) [S5]:13( 590.8047)
[S4]:7( 546.2866) [S3]:5( 364.1910) [S2]:3( 182.0955) [S1]:1( 0.000000)

[02.04] K-grid lattice
======================

Compatible Grid is 2D
B1 [rlu]= 0.000000 0.166667 0.000000
B2 = 0.166667 0.000000 0.000000
Grid dimensions : 6 6
K lattice UC volume [au]: 0.0015

[02.05] Energies [ev] & Occupations
===================================

Fermi Level [ev]:-0.996816
Electronic Temp. [ev K]: 0.000 0.000
Bosonic Temp. [ev K]: 0.000 0.000
States summary : Full Metallic Empty
0001-0056 0057-0100
Indirect Gaps [ev]: 0.949779 3.604470
Direct Gaps [ev]: 0.949779 6.044160
X BZ K-points : 36
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Here I ignore the 36 kpoint list

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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

[BSE] Kernel dimension : 88704
[BSE] Exchange components : 25113

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

[RESTARTer] Section(s) completed for ./SAVE//db.em1s :1

[RD./SAVE//db.em1s]-----------------------------------------
Brillouin Zone Q/K grids (IBZ/BZ): 20 36 18 36
RL vectors (WF): 25113
Electronic Temperature [K]: 0.000000
Bosonic Temperature [K]: 0.000000
Static diel. fun. energies :Perdew & Wang (xc)
wavefunctions :Perdew & Wang (xc)
X matrix size : 139
X band range : 1 100
X e/h energy range [ev]:-1.000000 -1.000000
X Time ordering :t
X xc-Kernel :none
X Drude frequency : 0.000 0.000
X poles [o/o]: 100.0000
Rl vectors in the sum : 25113
[r,Vnl] included :yes
Longitudinal Gauge :no
Field direction :0.1000E-4 0.000 0.000
BZ energy Random IM :no
BZ energy RIM points :0
:: Current Q-pt index : 1
:: X energy range [ev]: 0.000 0.000
:: X damping range [ev]:0.1000E-2 0.1000E-2
:: Number of frequencies : 1
- S/N 001132 ---------------------------- v.03.02.02 r.633 -

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

[05] BSE solver(s)
==================


[06] Game Over & Game summar

I try to create standart output with "yambo>&/dev/null" and get error message ad file unit number.




BY the way I have problem posted before about not using plasman-pole approximation. I still have some problem. I copied the problem from there:

The experimental band gap is electrochemical band gap( same as optical band gap?). I do not have measured data of photoemmision band gap. Roughly say how much difference are two band gaps? I am sorry I do not have measured plasma frequency. In the calculation I used PPAPntXPp=27.21138 eV. I read the yambo paper it said Plasmon-pole approximation can be questionable when some of valence orbitals are spatially localized (like in d or f metals). It is also said the metallic screening (noble and transition metals) does not make the RPA meaningful. I think Sc may be belong to it. However, Sc in Sc4C2@C80 donate 3 electron/per Sc atom. Therefore Sc become ion with no d electron outside. So I am not sure whether Sc is the reason caused the trouble.

Another posibility is to do coulomb cutoff. The molecule is about 8A. Sc4C2@C80 has a core Sc4C2 with +6 electron charge inside C80 which has -6 electron charge. I used supercell 12A x 12A x12A. I do not have the experience whether I need consider to do Coulomb cutoff for GW calculation.

I will give a try to use COHSEX. However, I am not a developer. I cannot use : svn checkout svn+ssh://developername@scm.qe-forge.org/svn/yambo. In Abinit there is a GW lesson two about beyond PPA. Is it same as that of yambo CHOSEX.

Thank you again

Zhifan Chen
Dept. of Physics
Clark Atlanta University
USA

[Daniele Varsano]

Dear Zhifan,
a possibility is that your database containing the screening (db.em1s) is corrupted.
You can try to remove it and calculate the screening from scratch.

Anyway, why you calculate a screening with 139 block size and
do not use it in the BSE:
BSENGBlk= 1 RL # [BSK] Screened interaction block size

Note that this is not the source of the error you are experiencing, but anyway this is
variable that have to be checked to be at convergence.

Roughly say how much difference are two band gaps?

It depend strongly of the properties of your system. The BS equation aims to describe bound excitons,
so, the difference between the two gaps is the binding energy of the exciton (if you are in presence of bound
excitons!!).

. I do not have the experience whether I need consider to do Coulomb cutoff for GW calculation.

You want to treat an isolate molecule?? so why you have a k-point sampling?? Sorry, here I so not understand!!

In Abinit there is a GW lesson two about beyond PPA. Is it same as that of yambo CHOSEX.

Not at all!!! Careful, cohsex is an approximation for the self energy which neglect dynamical screening, so
it is not at all beyond PPA!!! Let's say, that cohsex is an approx rougher than the GW.

Cheers,

Daniele

[andrea marini]

I am not a developer. I cannot use : svn checkout svn+ssh://developername@scm.qe-forge.org/svn/yambo.

Why do you say so ? Even if you are not a developer you are more then welcome to use svn. Svn is for anyone that want to be constantly updated about the last releases of the code. Give it a try!

[zchen]

Dear Drs Marini and Varsano:
Thanks. I think the problem is caused by kptopt in Abinit. Two dimension example of Si in yambo used two set of k point. I used 6X6X1 for the first group. I also used 6x6x1 for the second set. However for second k point set I used kptopt=2. According to the manual this is to be used when preparing a RF calculation at q=(0,0,0) . After get KSS file I introduce it to yambo. I found no error in calculating the following command
yambo -i -V 1
yambo -o c
yambo -o c -t a
yambo -b
When doing yambo -i -V 1, I got message:2 equivalent points in the rlu grid found X grid is not uniform Gamma point only. I think for the optical absorption we need Gamma point. rpa and alda data has no problem.
However to run yambo -o b -y h comman I get message:2 equivalent points in the rlu grid found X grid is not uniform Gamma point only.0:SHAPE:arg not associated with array.
Also I can not do GW calculation. It seems there is some thing wron to use kptopt=2.

I tried the command
svn checkout svn+ssh://developername@scm.qe-forge.org/svn/yambo
and get message ssh:scm.qe.forge.org:name or service not known
svn: connection closed unexpectelly.


Zhifan Chen
Clark Atlanta University
USA

[andrea marini]

I tried the command
svn checkout svn+ssh://developername@scm.qe-forge.org/svn/yambo
and get message ssh:scm.qe.forge.org:name or service not known
svn: connection closed unexpectelly.

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