Fermi level on the coarse grid always 0?

[chrisewolf]

Hi all,

just a quick question: is it normal that the fermi level on the coarse grid is always reported as 0.0 eV? I wannierize all bands (no bands skipped) and the fermi level on the fine grid is calculated properly (it is the same as the "highest occupied level" from the nscf run), but in the output I always find that


Fermi energy coarse grid = 0.000000 eV

This is a 1L MgO with 2 Mg and 2 O and 20 A of vacuum on top.

Code: Select all

     bravais-lattice index     =            6
     lattice parameter (alat)  =       7.9689  a.u.
     unit-cell volume          =    3036.3119 (a.u.)^3
     number of atoms/cell      =            4
     number of atomic types    =            2
     number of electrons       =        32.00
     number of Kohn-Sham states=           16
     kinetic-energy cutoff     =     120.0000  Ry
     charge density cutoff     =     480.0000  Ry
     Exchange-correlation      = PBE ( 1  4  3  4 0 0)

     celldm(1)=   7.968900  celldm(2)=   1.000000  celldm(3)=   6.000000
     celldm(4)=   0.000000  celldm(5)=   0.000000  celldm(6)=   0.000000


...

     highest occupied level (ev):    -4.9385

Code: Select all

     Using random q-mesh:       100000
     Size of q point mesh for interpolation:     100000
      Using k-mesh file: meshes/MGXM.dat
     Size of k point mesh for interpolation:        404
     Max number of k points per pool:                8

     Fermi energy coarse grid =   0.000000 eV

     Fermi energy is calculated from the fine k-mesh: Ef =  -4.874877 eV

     Warning: check if difference with Fermi level fine grid makes sense

     ===================================================================

              ibndmin =    11  ebndmin =    -0.579
              ibndmax =    16  ebndmax =    -0.363

Code: Select all

--
&inputepw
  prefix      = 'mgo'
  amass(1) = 24.30500
  amass(2) = 15.99900 
  outdir      = './'
  etf_mem     = 0

  iverbosity  = 0
  system_2d   = .true.

  elph        = .true.
  epbwrite    = .true.
  epbread     = .false.

  epwwrite    = .true.
  epwread     = .false.

  wannierize  = .true.
  nbndsub     =  16
  nbndskip    =  0
  num_iter    = 300
  iprint      = 2
  proj(1)     = 'O:s;p'  
  proj(2)     = 'Mg:s;p'
  wdata(1) = 'bands_plot = .true.'
  wdata(2) = 'begin kpoint_path'
  wdata(3) = 'M 0.50000    0.50000    0.00000  G  0.00000    0.00000    0.00000'
  wdata(4) = 'G 0.00000    0.00000    0.00000  X  0.50000    0.00000    0.00000'
  wdata(5) = 'X 0.50000    0.00000    0.00000  M  0.50000    0.50000    0.00000 '
  wdata(7) = 'end kpoint_path' 
  wdata(8) = 'write_hr=.false.'
  wdata(9) = 'write_hr_diag = .true.'

  elecselfen  = .true.
  phonselfen  = .false.
  a2f         = .false.

  specfun_el   = .true. 
  specfun_ph   = .false.
  wmin_specfun = -4
  wmax_specfun = 1
  nw_specfun   = 101
  
  band_plot   = .true. 
  asr_typ     = 'simple'
  lpolar      = .true.
  prtgkk        =.false.

  efermi_read = .false. 
  !fermi_energy =  -4.9385

  parallel_k  = .true.
  parallel_q  = .false.

  fsthick     = 3 ! eV 
  eptemp      = 1 ! K
  degaussw    = 0.1 ! eV

  dvscf_dir   = '../phonon/save'
  filukk      = './mgo.ukk'

  !filqf       = 'meshes/MGXM.dat'
  filkf       = 'meshes/MGXM.dat'

  rand_q      = .true.
  rand_nq     = 1000000

  !rand_k      = .true.
  !rand_nk     = 1000000

  !nkf1        = 50
  !nkf2        = 50
  !nkf3        = 50
  

  nk1         = 8
  nk2         = 8
  nk3         = 1

  nq1         = 4
  nq2         = 4
  nq3         = 1
/
  6 cartesian
         0.000000000   0.000000000   0.000000000
         0.000000000   0.250000000   0.000000000
         0.000000000  -0.500000000   0.000000000
         0.250000000   0.250000000   0.000000000
         0.250000000  -0.500000000   0.000000000
        -0.500000000  -0.500000000   0.000000000 

Wannierization of bands and interpolation of phonons in this system look perfect; none of the previous problems I had encountered with the bulk appeared!

TIA for any help on this and a nice weekend!
Chris

[sponce]

Hello Chris,

This is because you do a restart calculation (some information are lost/not recomputed in that case).

If you do a full run, you should have the coarse grid Fermi information.

Also note that in the case of a restart, only the fine grid Fermi level matter/is used.

Best,
Samuel

[chrisewolf]

Than you for the swift and reassuring reply, sometimes I get overly paranoid about what the code is doing when I am not watching...

With regard to 2D systems, do you have any recommendation which parameters to increase first when trying to converge? Above input gives me too high Im(Sigma) (2-3 orders higher than the bulk MgO) and increasing the fine grid or random k/q points does not seem to make a difference. Is the 2D case that much more demanding with respect to the nk and nq of the nscf and phonon run? Phonons and bands are nicely reproduced...

Best,
Chris

[sponce]

Hello,

See my reply to your other post.

Cheers,
Samuel

[chrisewolf]

Just saw it, thanks Samuel!