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can't find the correct band gap.

Vj
2017-11-24
2017-12-08
  • Vj

    Vj - 2017-11-24

    Dear Developers,

    I'm working on Cu2O and using the GGA-PBE calculation I'm not getting the correct band gap, so from other paper references, I'm using GGA+U. The parameters are U=6eV and J=1eV from VASP code, but from elk I cann't find the correct bandgap of it, which is 2.17 eV(experimental). what is wrong in my calculation please guide me.

    ELK.IN

    tasks
    0

    xctype
    20, 0, 0

    dft+u
    2 1 : dftu, inpdftu
    1 2 0.22049 0.036748 : is, l, U, J

    spinpol
    .true.
    avec
    1.0000 0.0000 0.0000
    0.0000 1.0000 0.0000
    0.0000 0.0000 1.0000
    scale
    8.069241
    rgkmax
    8.5
    lmaxapw
    10
    gmaxvr
    14.0
    sppath
    '../../../../../species/'
    atoms
    2 : nspecies
    'Cu.in' : spfname
    4 : natoms; atposl, bfcmt below
    0.0 0.0 0.0 0.0 0.0 0.0
    0.0 0.5 0.5 0.0 0.0 0.0
    0.5 0.5 0.0 0.0 0.0 0.0
    0.5 0.0 0.5 0.0 0.0 0.0
    'O.in' : spfname
    2 : natoms; atposl, bfcmt below
    0.25 0.25 0.25 0.0 0.0 0.0
    0.75 0.75 0.75 0.0 0.0 0.0
    ngridk
    32 32 32
    plot1d
    3 200 : nvp1d, npp1d
    0.5 0.0 0.0 L : vlvp1d
    0.0 0.0 0.0 ~G
    0.5 0.5 0.0 X
    nempty
    8

    Thank you

     
  • Eike Schwier

    Eike Schwier - 2017-12-04

    Dear Vj,

    I am not a developer, but from your input file I suspect that you are missing an initial magnetic field for you spinpol=true calculations. I assume CuO is in an AFM state so it would be a good start to use moments inside the MT of copper. As a reference you can check the Fe-AMF example in the magnetism folder of elk.

    best,
    Eike

     
  • Vj

    Vj - 2017-12-08

    Thank you Eike.
    I'm use it as you say but I want to know can we tune the Band gap with the value of U in DFT+U calculation. The band gap is not well when I'm not using the spinpol=true, what is a correct way to calculation, please guide me.

    Thank you

     

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