[QE-users] Wrong position of fermi level in bulk Cr2O3

[Yuvam Bhateja]

Hello dear experts,
Hope you are doing well.

I was trying to calculate the DOS in hexagonal Cr2O3, the DOS is coming
very well with a bandgap of 3.09, but the problem is the Fermi level is at
the edge of LUMO whereas I've observed that it should be at HUMO edge in
few already published papers.
I used PBE NC SR pseudopotential and also optimized with the same. I used
gaussian smearing with a width of 0.001 in VC-relax and tetrahedra in SCF
calculation.

Here is my input file -

&CONTROL
    calculation   = "scf"
    pseudo_dir    = "./"
    outdir        = "./outdir"
/

&SYSTEM
    a                         =  4.6166825e+00
    c                         =  1.2457778e+01
    ecutrho                   =  4.5000e+02
    ecutwfc                   =  4.5000e+01
    ibrav                     = 4
    nat                       = 30
    nspin                     = 2
    ntyp                      = 3
    nbnd                      = 276
    starting_magnetization(1) = 0.5
    starting_magnetization(2) = -0.5
    starting_magnetization(3) = 0.0
    tot_magnetization         = 0.0
    lda_plus_u                = .true.
    Hubbard_U(1)              = 4.7
    Hubbard_U(2)              = 4.7
    Hubbard_J0(1)             = 1
    Hubbard_J0(2)             = 1
/

&ELECTRONS
    conv_thr         =  1.00000e-11
    electron_maxstep = 2000
    mixing_beta      =  7.00000e-01
    startingpot      = "atomic"
    startingwfc      = "atomic+random"
/


K_POINTS {automatic}
 12 12 12  0 0 0

ATOMIC_SPECIES
Cr1    51.99610  Cr.upf
Cr2    51.99610  Cr.upf
O      15.99940  O.upf

ATOMIC_POSITIONS (angstrom)
Cr2          -0.0000027528        2.6654550870        3.9638155751
Cr1           2.3083528721        1.3327252495        2.2651020880
Cr1          -0.0000027528        2.6654550870        0.1887989665
Cr2           0.0000000000        0.0000000000        1.8875092202
Cr2           0.0000000000        0.0000000000        8.1164268017
Cr1          -0.0000027528        2.6654550870        6.4177165986
Cr1           0.0000000000       -0.0000000000        4.3414084067
Cr2           2.3083528721        1.3327252495        6.0401185402
Cr2           2.3083528721        1.3327252495       12.2690363475
Cr1           0.0000000000        0.0000000000       10.5703258606
Cr1           2.3083528721        1.3327252495        8.4940197683
Cr2          -0.0000027528        2.6654550870       10.1927331413
O             1.4445126756        0.0000000398        3.1144588851
O             3.0306076646        0.0817435268        1.0381518347
O             0.8638388763        1.3327251470        1.0381518347
O             3.0306056520        2.5837116627        1.0381518347
O            -0.7222568310        1.2509851988        3.1144588851
O             1.5860942747        2.7471960155        3.1144588851
O             3.7528623252        1.3327254382        7.2670694393
O             0.7222547656        1.4144695631        5.1907658203
O            -1.4445122603        2.6654550733        5.1907658203
O             0.7222574947        3.9164369542        5.1907658203
O             1.5860961469        2.5837115564        7.2670694393
O             1.5860937210        0.0817433419        7.2670694393
O             1.4445122976        2.6654551364       11.4196834856
O            -1.5860942579        2.7471959172        9.3433763434
O             0.8638382678        3.9981804108        9.3433763434
O             0.7222569078        1.2509852624        9.3433763434
O            -0.7222575680        3.9164369549       11.4196834856
O            -0.7222547296        1.4144694992       11.4196834856


I later tried with pw91 USPP, it fixed the fermi level position (it's now
at HUMO edge) but the bad gap is now very underestimated to 2.3 eV.

I tried paw but it wasn't working with me.

Can someone please help?

Regards
Yuvam Bhateja
IIEST Shibpur
India
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