optical spectrum

[samaneh]

Dear Developers,
I calculated the band structure (G0W0 using yambo -g n -p p) and optical absorption (RPA using yambo -o c -k hartree)
with the same conditions (nbnds, maxGvec, NGs,..but these are not the converged data)
and the results are not consistent
I mean the spectrum is as I expect it
but the band structure is not right!
Is that possible?
and if yes, does it mean that the converged parameters
for optical spectrum are different from the G0W0 calculations?
Best regards
S. Ataei, Department of Physics, University of Tehran, Iran

[samaneh]

Dear Developers,
related to my previous post,
as mentioned before
" COHSEC correction applies to the energies but not to the wave functions (molecular orbitals), which implies the assumptions that COHSEX orbitals are the same of KS orbitals."
for G0W0 calculations(first order approximation) both of energies and orbitals are corrected or in this case it is like the COHSEX?
Thank you in advance
S. Ataei

[myrta gruning]

Dear Samaneh,

1. in the GW approximation only the energies are corrected.
I would suggest to take a look at http://www.yambo-code.org/theory/index.php and http://www.yambo-code.org/theory/lectures.php to see the equations that are solved by yambo and what exactly is calculated. This will give you as well insight in the convergence parameters.

2. Convergence parameters for BSE and GW are not necessarily the same.

3. To give you a better answer, we need more details on the calculations. What do you mean by 'wrong' and what exactly did you calculate? A GW calculation gives as output the correction at the k point of your grid. Are you referring to those values or did you use the post-processing tool for getting the band structure? In the latter case you need to pay attention as the tool is not working for systems with time reversal symmetry. Let us know.

Regards,
m

[samaneh]

Dear myrta ,
Thank you for your help
I have a defected TiO2 structure
and it is expected that the defect level
should be filled but when I calculate QP band structure
using ypp the defect level is empty!
while the absorption spectrum is OK for it
(I mean it has a related peak to the defect level)
using the same parameters as the G0W0 calculation!
Best regards
S. Ataei

[myrta gruning]

Dear Samaneh

does your system have time-reversal symmetry, you can check this in one of the reports of the calculations under

Code: Select all

 [02.02] Symmetries

if yes, did you remove it?

what about the corrections from the GW calculation? do they look OK?
for how many k-points/bands did you calculate the corrections? ypp is doing an interpolation, so it needs enough points to give a reasonable result.

[samaneh]

Dear myrta,
This section for my job is:
[02.02] Symmetries
==================

DL (S)ymmetries [cc]
[S1] 1.00 0.00 0.296E-09 0.00 1.000 0.00 0.296E-09 0.00 1.00
[S2] 1.00 0.00 0.296E-09 0.00 ********* 0.00 0.296E-09 0.00 1.00

[SYMs] Time-reversal derived K-space symmetries: 3 4
[SYMs] Spatial inversion 3 is NOT a symmetry
[SYMs] Group table built correctly

and I do not know how and why should I remove it?
the k points in the DFT calculations in this test are less than the converged one
but in the ypp input I used all of the high symmetry points.
Best regards
S. Ataei

[myrta gruning]

Dear Samaneh,

To sum up:
1. as soon as your parameters are well converged the results from the GW calculations should be fine. You can inspect the report or the o.QP file where the corrections to the Kohn-Sham eigenvalues for the k and bands you selected are reported. If the k-point mesh you are using contains 'useful' k-points you can already extract several information from this file, even without plotting the band structure. Did you check those results? Are they OK?

2. The plotting of the bandstructure is a post-processing operation. The calculated KS bandstructure and GW corrections are used and the GW bandstructure is obtained by interpolation. Note that interpolation introduces additional error and its quality depends on the data you are providing (e.g. the number of GW corrected states). The error in interpolation can be checked by plotting the interpolated DFT bands (output of ypp) against the calculated DFT bands (e.g. from a non-self consistent DFT).

3. Unfortunately at the moment the postprocessing tool does NOT support time-reversal symmetry. Then if the system has time-reversal symmetry the postprocessing will output incorrect results. One then needs to re-run the calculations without the time-reversal symmetry. This can be done either by performing DFT calculations without the time-reversal or by using the ypp utility in the "remove-symmetry" mode.

4. Finally, which version of yambo are you using? (please report this every time you report a problem) It seems there are issues with the latest version as well. viewtopic.php?f=9&t=1051&p=4762&hilit=reversal#p4762. Let me know so I can you further.

[samaneh]

Dear Dr. Myrta,
Thank you for your helpful comments
I use yambo "GPL Version 3.4.1 Revision 3187"
and in the ypp file it does not contain RmTimeRev variable!
Ok I should check my kpoints.
but I run yambo -g n -p p & yambo with more kpoints
and after 2 hours it stoped (here is the end of the r_emld_ppa file)

[WR./SAVE//db.pp]-------------------------------------------
Brillouin Zone Q/K grids (IBZ/BZ): 80 216 80 216
RL vectors (WF): 999
Coulomb cutoff potential :none
Electronic Temperature [K]: 299.9765
Bosonic Temperature [K]: 299.9765
PPA diel. fun. energies :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
wavefunctions :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
Global Gauge :length
X matrix size : 35
X band range : 1 200
X e/h energy range [ev]:-1.000000 -1.000000
X Time ordering :c
X xc-Kernel :none
X Drude frequency : 0.00 0.00
X poles [o/o]: 100.0000
Rl vectors in the sum : 999
[r,Vnl] included :yes
Field direction :0.1000E-4 0.000 0.000
BZ energy Random IM :no
BZ energy RIM points :0
PPA Im energy [ev]: 27.21138
- S/N 008589 --------------------------- v.03.04.01 r.3187 -
[X-CG] R(p) Tot o/o(of R) : 749913 4353321 100
[X-CG] R(p) Tot o/o(of R) : 750001 4353282 100
[X-CG] R(p) Tot o/o(of R) : 702634 4353325 100
[X-CG] R(p) Tot o/o(of R) : 753951 4353315 100
[X-CG] R(p) Tot o/o(of R) : 706462 4353314 100
[X-CG] R(p) Tot o/o(of R) : 706181 4353315 100
[X-CG] R(p) Tot o/o(of R) : 754723 4353313 100
[X-CG] R(p) Tot o/o(of R) : 754161 4353228 100
[X-CG] R(p) Tot o/o(of R) : 706814 4353332 100
[X-CG] R(p) Tot o/o(of R) : 707006 4353320 100
[X-CG] R(p) Tot o/o(of R) : 754112 4353332 100
[X-CG] R(p) Tot o/o(of R) : 703053 4353336 100
[X-CG] R(p) Tot o/o(of R) : 749467 4353336 100
[X-CG] R(p) Tot o/o(of R) : 749772 4353336 100
[X-CG] R(p) Tot o/o(of R) : 702737 4353336 100
[X-CG] R(p) Tot o/o(of R) : 750895 4353308 100
[X-CG] R(p) Tot o/o(of R) : 753508 4353314 100
[X-CG] R(p) Tot o/o(of R) : 753426 4353313 100
[X-CG] R(p) Tot o/o(of R) : 750590 4353312 100
[X-CG] R(p) Tot o/o(of R) : 753734 4353312 100
[X-CG] R(p) Tot o/o(of R) : 752765 4353312 100
[X-CG] R(p) Tot o/o(of R) : 707186 4353319 100
[X-CG] R(p) Tot o/o(of R) : 709972 4353319 100
[X-CG] R(p) Tot o/o(of R) : 709276 4353319 100
[X-CG] R(p) Tot o/o(of R) : 707819 4353317 100
[X-CG] R(p) Tot o/o(of R) : 710050 4353319 100
[X-CG] R(p) Tot o/o(of R) : 709526 4353317 100
[X-CG] R(p) Tot o/o(of R) : 707616 4353328 100
[X-CG] R(p) Tot o/o(of R) : 710187 4353330 100
[X-CG] R(p) Tot o/o(of R) : 709948 4353328 100
[X-CG] R(p) Tot o/o(of R) : 707811 4353330 100
[X-CG] R(p) Tot o/o(of R) : 710090 4353328 100
[X-CG] R(p) Tot o/o(of R) : 710049 4353330 100
[X-CG] R(p) Tot o/o(of R) : 749167 4353336 100
[X-CG] R(p) Tot o/o(of R) : 753181 4353336 100
[X-CG] R(p) Tot o/o(of R) : 753365 4353336 100
[X-CG] R(p) Tot o/o(of R) : 750445 4353336 100
[X-CG] R(p) Tot o/o(of R) : 752689 4353336 100
[X-CG] R(p) Tot o/o(of R) : 752659 4353336 100
[X-CG] R(p) Tot o/o(of R) : 749932 4353271 100
[X-CG] R(p) Tot o/o(of R) : 753721 4353311 100
[X-CG] R(p) Tot o/o(of R) : 753127 4353275 100
[X-CG] R(p) Tot o/o(of R) : 749880 4353319 100
[X-CG] R(p) Tot o/o(of R) : 753876 4353275 100
[X-CG] R(p) Tot o/o(of R) : 752969 4353321 100
[X-CG] R(p) Tot o/o(of R) : 707870 4353328 100
[X-CG] R(p) Tot o/o(of R) : 709526 4353330 100
[X-CG] R(p) Tot o/o(of R) : 709795 4353328 100
[X-CG] R(p) Tot o/o(of R) : 707364 4353330 100
[X-CG] R(p) Tot o/o(of R) : 710388 4353328 100
[X-CG] R(p) Tot o/o(of R) : 709336 4353330 100
[X-CG] R(p) Tot o/o(of R) : 707739 4353322 100
[X-CG] R(p) Tot o/o(of R) : 710494 4353332 100
[X-CG] R(p) Tot o/o(of R) : 710759 4353324 100
[X-CG] R(p) Tot o/o(of R) : 706603 4353336 100
[X-CG] R(p) Tot o/o(of R) : 709531 4353324 100
[X-CG] R(p) Tot o/o(of R) : 709694 4353336 100
[X-CG] R(p) Tot o/o(of R) : 749640 4353332 100
[X-CG] R(p) Tot o/o(of R) : 753493 4353336 100
[X-CG] R(p) Tot o/o(of R) : 753402 4353336 100
[X-CG] R(p) Tot o/o(of R) : 750494 4353336 100
[X-CG] R(p) Tot o/o(of R) : 753527 4353336 100
[X-CG] R(p) Tot o/o(of R) : 753529 4353336 100
[X-CG] R(p) Tot o/o(of R) : 702961 4353324 100
[X-CG] R(p) Tot o/o(of R) : 748733 4353324 100
[X-CG] R(p) Tot o/o(of R) : 749504 4353320 100
[X-CG] R(p) Tot o/o(of R) : 702616 4353324 100
[X-CG] R(p) Tot o/o(of R) : 754518 4353332 100
[X-CG] R(p) Tot o/o(of R) : 707058 4353336 100
[X-CG] R(p) Tot o/o(of R) : 707202 4353334 100
[X-CG] R(p) Tot o/o(of R) : 753990 4353336 100
[X-CG] R(p) Tot o/o(of R) : 754200 4353336 100
[X-CG] R(p) Tot o/o(of R) : 706232 4353336 100
[X-CG] R(p) Tot o/o(of R) : 707112 4353334 100
[X-CG] R(p) Tot o/o(of R) : 754442 4353336 100
[X-CG] R(p) Tot o/o(of R) : 702830 4353328 100
[X-CG] R(p) Tot o/o(of R) : 750266 4353336 100
[X-CG] R(p) Tot o/o(of R) : 749784 4353332 100
[X-CG] R(p) Tot o/o(of R) : 702640 4353336 100

CpuTiming [Min/Max/Average]: 01h-39m-02s/01h-51m-45s/01h-51m-16s

[08] Game Over & Game summary
=============================

YAMBO@node194 x 080 CPUs * 08/06/2015 08:40 [start]
08/06/2015 11:29 [end]

Cpu Timing [Min/Max/Average]: 02h-03m-23s/02h-16m-23s/02h-15m-49s

.-ACKNOWLEDGMENT
|
| The users of YAMBO have little formal obligations with respect to
| the YAMBO group (those specified in the GNU General Public
| License, http://www.gnu.org/copyleft/gpl.txt). However, it is
| common practice in the scientific literature, to acknowledge the
| efforts of people that have made the research possible. In this
| spirit, please find below the reference we kindly ask you to use
| in order to acknowledge YAMBO:
|
| Yambo: An ab initio tool for excited state calculations
| A. Marini, C. Hogan, M. Gr"uning, D. Varsano
| Computer Physics Communications 180, 1392 (2009).
|

.-Input file : yambo.in
| em1d # [R Xd] Dynamical Inverse Dielectric Matrix
| ppa # [R Xp] Plasmon Pole Approximation
| HF_and_locXC # [R XX] Hartree-Fock Self-energy and Vxc
| gw0 # [R GW] GoWo Quasiparticle energy levels
| ElecTemp= 0.02585 eV # Electronic Temperature
| BoseTemp= 0.02585 eV # Bosonic Temperature
| FFTGvecs= 999 RL # [FFT] Plane-waves
| EXXRLvcs= 999 RL # [XX] Exchange RL components
| Chimod= "Hartree" # [X] IP/Hartree/ALDA/LRC/BSfxc
| % BndsRnXp
| 1 | 200 | # [Xp] Polarization function bands
| %
| NGsBlkXp= 1 Ry # [Xp] Response block size
| % LongDrXp
| 0.1000E-4 | 0.000 | 0.000 | # [Xp] [cc] Electric Field
| %
| PPAPntXp= 27.21138 eV # [Xp] PPA imaginary energy
| % GbndRnge
| 1 | 200 | # [GW] G[W] bands range
| %
| GDamping= 0.0037 eV # [GW] G[W] damping
| dScStep= 0.0037 eV # [GW] Energy step to evalute Z factors
| GwEnComp=-1.000000 eV # [GW] If <= 0 use 0-order EET; > 0 the Bruneval-Gonze terminator
| DysSolver= "" # [GW] Dyson Equation solver (`n`,`s`,`g`)
| %QPkrange # [GW] QP generalized Kpoint/Band indices
| 1| 80| 1|200|
| %
| %QPerange # [GW] QP generalized Kpoint/Energy indices
| 1| 80| 0.0|-1.0|
| %

but as it clear it considered NGsBlkXp= 1 Ry
while4 I choose NGsBlkXp= 7 Ry
in yambo.in!!!
I think maybe it is because of RAM problem
but how can I understand how much RAM do I need?
and then how should I use -M to allocating memory?
another question is that
if I use cohsex calculation (-p c)
is that possible to use its database in the input
file of BSE?
Thanks
Samaneh

[Daniele Varsano]

Dear Samaneh,
no, yambo does not reduce the G vector because of lack of RAM, he tries to to do what it is asked and eventually dies if the RAM is not enough.
Your input is very confusing, you have the same variables repeated many times, try to redo the calculation from scratch with a more clear input.
A suggestion:

Code: Select all

%QPkrange                    # [GW] QP generalized Kpoint/Band indices
  1| 80|  1|200|
%

are you sure you need to correct so many qp energies (16000!!!): it looks me too much and useless.
Finally, yes, you can use the cohsex database (ndb.QP) in the BSE in the same way you use the GW energies.

Best,
Daniele

[samaneh]

Dear Daniele,
Thank you for your helpful comments
but since I need to do bse calculation
I have to use all kpoints (80-the converged kpoints(just I plotted the RPA spectrum with different kpoints
and with 80 kpoints the shape of the spectrum becomes converged)) and also all bands (I have 100 valence bands
so I considered the same value for the empty states, I think this is not so much for empty states)!!!
Am I right????
or can I ignore some of the valence bands and do the G0W0 and after that BSE calculations ????
Best regards
S. Ataei