Hi, I am new with exciting code, and very interested in exx options.
My question is, if the exchange potential is averaged somehow spatially in the code or not?
the problem is that when i run Si with exx option(input file taken from examples,
xctype can be -1,-2,-3),
i remove degeneracy of lower occupied bands in X-W direction,that doesn't happen in lda or other exchange codes(Goerling results,for example).
How exx result depends on nempty number?how many unocc.bands should be included?
Or may be i am doing something wrong with input file?
here's my input:
!------------- INPUT -----------
! Band structure of silicon. The points listed after plot1d below are the
! vertices joined in the band structure.
Thanks for pointing this out. It is a known problem due to the fact that the interstitial density is symmetrized only with the point group of the crystal. The band degeneracy in question corresponds to an irreducible representation of the nonsymmorphic group. For LDA etc., this was not a problem because the splitting was so small, but OEP tries to break symmetry in any way it can. The problem is worse for Hartree-Fock since the effective non-local potential is not symmetrized at all.
However, this problem will be fixed in the next release. I'll send you an advance copy as soon as it's running.
Regards,
Kay.
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Hi, I am new with exciting code, and very interested in exx options.
My question is, if the exchange potential is averaged somehow spatially in the code or not?
the problem is that when i run Si with exx option(input file taken from examples,
xctype can be -1,-2,-3),
i remove degeneracy of lower occupied bands in X-W direction,that doesn't happen in lda or other exchange codes(Goerling results,for example).
How exx result depends on nempty number?how many unocc.bands should be included?
Or may be i am doing something wrong with input file?
here's my input:
!------------- INPUT -----------
! Band structure of silicon. The points listed after plot1d below are the
! vertices joined in the band structure.
tasks
0
10
20
avec
5.13 5.13 0.00
5.13 0.00 5.13
0.00 5.13 5.13
sppath
'/home2/dvolja/EXCITING/exciting/species/'
atoms
1 : nspecies
'Si.in' : spfname
2 : natoms
0.0 0.0 0.0 0.0 0.0 0.0 : atposl, bfcmt
0.25 0.25 0.25 0.0 0.0 0.0
xctype
-1
nempty
20
ngridk
2 2 2
vkloff
0.25 0.5 0.625
! These are the vertices to be joined for the band structure plot
plot1d
6 200 : nvp1d, npp1d
0.75 0.5 0.25 : vlvp1d
0.5 0.5 0.5
0.0 0.0 0.0
0.5 0.5 0.0
0.75 0.5 0.25
0.75 0.375 0.375
!--- end --
thank you very much,
Dmitri
Hi Dmitri,
Thanks for pointing this out. It is a known problem due to the fact that the interstitial density is symmetrized only with the point group of the crystal. The band degeneracy in question corresponds to an irreducible representation of the nonsymmorphic group. For LDA etc., this was not a problem because the splitting was so small, but OEP tries to break symmetry in any way it can. The problem is worse for Hartree-Fock since the effective non-local potential is not symmetrized at all.
However, this problem will be fixed in the next release. I'll send you an advance copy as soon as it's running.
Regards,
Kay.