degenerated energy

[hlshi]

Dear everyone:

I have test si g0w0, the pwscf and yambo are attached.

The question is, o.qp file results,

# Kpt Band Eo E-Eo Sc(Eo)
#
1.00000 1.00000 -12.08330 0.11445 5.30498
1.00000 2.00000 0.00000 -0.06349 -0.16498
1.000000 3.000000 0.000000 0.641024 -1.443307
1.000000 4.000000 0.000000 0.652097 -1.473218
1.000000 5.000000 2.572567 0.327843 -4.293787
1.000000 6.000000 2.572567 0.329697 -4.320966
1.000000 7.000000 2.572567 0.382350 -4.430470
1.000000 8.000000 3.518011 0.258437 -4.528199

the first kpoint is the Gamm point, according to the pwscf nscf output file si.band.out.,


For band 2,3,4, (p orbitals),they are degenerated (E0), after g0w0 correction, they should be still degenerated, however my result is not. Similarly, the Sc(E0) should be the same for them. I have tried diffrent convenged test using parameters (FFTGvecs,EXXRLvcs,NGsBlkXp), I can not get the degenerated results, furthmore, the gap deviates from the experimental gap further.

I have got the other's results for Si from the internet:
o.qp
#
# K-point Band Eo E-Eo Sc(Eo)
#
1.00000 1.00000 -12.04408 -1.62298 4.62448
1.000 2.000 -.6488E-4 0.5445 1.865
1.000 3.000 -.6488E-4 0.5412 1.861
1.000000 4.000000 0.000000 0.547782 1.868867
1.000000 5.000000 2.566559 1.764176 -2.163985
1.000000 6.000000 2.566592 1.753351 -2.176365
1.000000 7.000000 2.566592 1.754164 -2.175344
----------------------------------------------------------
This result is good,

Any suggestions, thanks in advance.

Dr. Shi hongliang

IHPC, a*star, Singapore

[hlshi]

Anyone knows, thanks very much.

Dr. Shi hongliang
IHPC, a*star, Singapore

[Daniele Varsano]

Dear Shi hongliang,
I had a look to the report file you included, and I can see problem also in the exchange part of the
self energy as well as the Vxc. What I suggest you is to perform a nscf calculation after the scf one.
This is the usual way for calculating the non occupied bands. I don't know if it is related to you
problem, but you can try it.

Cheers,

Daniele

[hlshi]

Dear Daniele Varsano:

Thanks.

You mean in the scf calculation I use the default nbnd parameter, then in the band (nscf) calculation, I use many emty bands(set detailed nbnd=200, for example ) .
I will try.

Dr. Shi hongliang
IHPC, a*star, Singapore

Dear Shi hongliang,
I had a look to the report file you included, and I can see problem also in the exchange part of the
self energy as well as the Vxc. What I suggest you is to perform a nscf calculation after the scf one.
This is the usual way for calculating the non occupied bands. I don't know if it is related to you
problem, but you can try it.

Cheers,

Daniele

[Daniele Varsano]

You mean in the scf calculation I use the default nbnd parameter, then in the band (nscf) calculation, I use many emty bands(set detailed nbnd=200, for example ) .

Yes, that's right.

Daniele

[hlshi]

Dear Daniele Varsano :

I sitll can not fix this problem according to your suggestion,
Thanks.

Dr. Shi hongliang
IHPC, a*star, Singapore

[Daniele Varsano]

Dear Hishi,

I have not clear ideas on what's going wrong.
The only supposition is something on the use of the symmetries of
your input file.
Try to activate the flag: force_symmorphic=.true. in the qe calculation.
And may try what happen putting your first atom in the origin:
Si 0.00 0.00 0.00
Si 0.25 0.25 0.25

please check also the celldm.

Next, where have you found the "correct" result? if there is also a report file,
we can easily check where are the relevant differences?

Cheers,

Daniele