Yambo Community Forum

Dear All
After obtaining QP spectra for my system I used ypp to get corrected DOS as follows
first I run ypp -s s and the run ypp, but the obtained dos is very little relative to GGA DOS ? Do I perform wrong with ypp option ?
best
Ali Kazempour ,Isfahan Univ .of Tech.,Iran

Dear Ali Kazempour

in order to obtain the QP density of states you have to use the comand

ypp -s s -V qp

and then read the QP database changing the line GfnQPdb= "none" in GfnQPdb= "E < SAVE/ndb.QP"

Dear Claudio
I did ypp -s s -V qp and change the line GfnQPdb= "none" in GfnQPdb= "E < SAVE/ndb.QP" and then run ypp , but it is similar to previous calculation and nothing is changed what can I do to get correct qp dos. and another qustion is why the hight of the qp dos is much less than GGA one?
best

Ali Kazempour ,Isfahan Univ .of Tech.,Iran

Dear Ali

do you have the file "SAVE/ndb.QP"?
if not it is normal that you get the same result,
moreover if you did not compile yambo with NetCDF (http://www.unidata.ucar.edu/software/netcdf/)
the name of the database will be "db.QP" and not "ndb.QP".

let me know

Claudio

Dear Claudio
I have db.QP in SAVE but again I got the wrong dos. Should I multiply qp DOS with somthing? for example for qp dos I have:
E qp-DOS
4.70373 0.08592
4.713729 0.103889
4.723730 0.102235
4.73373 0.09615
4.74373 0.08110
4.75373 0.06342
4.76373 0.06792
4.77373 0.09681
4.783735 0.121704
4.793736 0.128094
4.803736 0.141723

while for GGA DOS I have
4.700 0.7126E+01
4.710 0.7114E+01
4.720 0.7096E+01
4.730 0.7070E+01
4.740 0.7035E+01
4.750 0.6989E+01
4.760 0.6931E+01
4.770 0.6862E+01
4.780 0.6780E+01
4.790 0.6686E+01
4.800 0.6582E+01


Why Does these two differ so much??
best
Ali

Dear Ali

it is not so clear to me your problem, the qp-dos and cga-dos are different, this is normal.

Try a simpler case, a calculation with only one k-point (gamma point), and you will see immediatly the difference.

Moreover remember that if you have calculated the qp correction for a given set of bands, and then
you want the qp-dos for a larger number of bands, yambo uses an internal interpolation to generate the missing qp corrections.

Ohterwise put in the forum your input files, ground state and yambo input.

dear claudio
note that for example in energy 4.7 eV the dos value for qp is 0.08 and for gga is 7.1 . this difference is so much and it is seen for all value of the range.


yambo.in:
gw0 # [R GW] GoWo Quasiparticle energy levels
ppa # [R Xp] Plasmon Pole Approximation
HF_and_locXC # [R XX] Hartree-Fock Self-energy and Vxc
em1d # [R Xd] Dynamical Inverse Dielectric Matrix
EXXRLvcs= 2969 RL # [XX] Exchange RL components
% QpntsRXp
1 | 148 | # [Xp] Transferred momenta
%
% BndsRnXp
1 | 100 | # [Xp] Polarization function bands
%
NGsBlkXp= 1 RL # [Xp] Response block size
% LongDrXp
1.000000 | 0.000000 | 0.000000 | # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138 eV # [Xp] PPA imaginary energy
% GbndRnge
1 | 100 | # [GW] G[W] bands range
%
GDamping= 0.10000 eV # [GW] G[W] damping
dScStep= 0.10000 eV # [GW] Energy step to evalute Z factors
%QPkrange # [GW] QP generalized Kpoint/Band indices
1|148| 1|100|
%
%QPerange # [GW] QP generalized Kpoint/Energy indices
1|148| 0.0|-1.0|


and ypp.in is

dos # [R] DOS
electrons # [R] Electrons (and holes)
GfnQPdb= "E < SAVE/db.QP" # [EXTQP G] Database
GfnQP_N= 1 # [EXTQP G] Interpolation neighbours
% GfnQP_E
0.000000 | 1.000000 | 1.000000 | # [EXTQP G] E parameters (c/v)
%
% GfnQP_W
0.000 | 0.000 | 0.000 | 0.000 | # [EXTQP G] W parameters (c/v)
%
GfnQP_Z= ( 1.000000 , 0.000000 ) # [EXTQP G] Z factor (c/v)
DOS_broad= 0.10000 eV # Broadening of the DOS
DOS_bands= 100 # DOS bands

thanks a lot

Dear Ali

you are right.

I checked your input file, but I didn't notice anything strange, except

NGsBlkXp= 1 RL # [Xp] Response block size

remember that you have to converge your calculations respect to the block size,
and 1 is not a converged result, so increase it until the quasi-particle energies do not change anymore.

Ali send also the o.qp file and the ground state ones,
at the moment I have no idea what went wrong.

Claudio

Dear claudio
I increased the NGsBlkXp to 150 ,but the problem didn't solve.
yambo.in:
gw0 # [R GW] GoWo Quasiparticle energy levels
ppa # [R Xp] Plasmon Pole Approximation
HF_and_locXC # [R XX] Hartree-Fock Self-energy and Vxc
em1d # [R Xd] Dynamical Inverse Dielectric Matrix
EXXRLvcs= 2969 RL # [XX] Exchange RL components
% QpntsRXp
1 | 148 | # [Xp] Transferred momenta
%
% BndsRnXp
1 | 100 | # [Xp] Polarization function bands
%
NGsBlkXp= 150 RL # [Xp] Response block size
% LongDrXp
1.000000 | 0.000000 | 0.000000 | # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138 eV # [Xp] PPA imaginary energy
% GbndRnge
1 | 100 | # [GW] G[W] bands range
%
GDamping= 0.10000 eV # [GW] G[W] damping
dScStep= 0.10000 eV # [GW] Energy step to evalute Z factors
%QPkrange # [GW] QP generalized Kpoint/Band indices
1|148| 1|100|
%
%QPerange # [GW] QP generalized Kpoint/Energy indices
1|148| 0.0|-1.0|


ypp.in:

dos # [R] DOS
electrons # [R] Electrons (and holes)
GfnQPdb= "E < SAVE/db.QP" # [EXTQP G] Database
GfnQP_N= 1 # [EXTQP G] Interpolation neighbours
% GfnQP_E
0.000000 | 1.000000 | 1.000000 | # [EXTQP G] E parameters (c/v)
%
% GfnQP_W
0.000 | 0.000 | 0.000 | 0.000 | # [EXTQP G] W parameters (c/v)
%
GfnQP_Z= ( 1.000000 , 0.000000 ) # [EXTQP G] Z factor (c/v)
DOS_broad= 0.10000 eV # Broadening of the DOS
DOS_bands= 100 # DOS bands

I also get converged qp states for si as a example but i cannot obtain correct dos. WHY? may be I should multiply with somthing?
BEST

Dear Ali

some comment about your input files:

1) scf.in
remove nosym=.true. why you don't want to use the symmetries?
if you use them the calculations will be faster

2) bands.in
please do not use

calculation = 'bands'
but
calculation = 'nscf'

'bands' is not well supported in PWSCF.
Then remove nosym=.true. and put force_symmorphic=.true.

see discussion here: viewtopic.php?f=7&t=25

for the GW calculation only a restricted set of symmetries can be used.

Then remember that when you perform a 'bands' or 'nscf' calculation with ESPRESSO
the cutoff is "diago_thr_init = 1.0d-8" and not "conv_thr = 1.0d-8" !!!!
conv_thr has to be used only in 'scf' self-consistent calculation, see the ESPRESSO
input file /espresso-4.1.3/Doc/INPUT_PW.txt

3) please use a standard pseudopotential for example Si.pz-vbc.UPF
that you can find here: http://www.quantum-espresso.org/pseudo/1.3/html/Si.html

I checked the calculation and now everything works fine, I put in the attachment
the correct input files and a small calculation with only 10 bands,
remember to check the convergence on number of bands, block-size, cutoff etc..

Claudio