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Hartree-Fock convergence

Elk Users
Stefano
2015-08-14
2015-08-18
  • Stefano

    Stefano - 2015-08-14

    Hi,

    I have some problem converging an HF calculation. This is the input file

    tasks
    0
    5
    10

    dos
    6000 100 1
    -1.0 1.0

    swidth
    0.001

    nempty
    8

    avec
    1.00 1.00 0.00
    1.00 0.00 1.00
    0.00 1.00 1.00

    scale
    3.9468

    sppath
    '../../species/'

    spinpol
    .false.

    atoms
    2 : nspecies
    'Ni.in' : spfname
    1 : natoms
    0.0 0.0 0.0 0.0 0.0 0.0 : atposl, bfcmt
    'O.in' : spfname
    1 : natoms
    0.5 0.5 0.5 0.0 0.0 0.0

    ngridk
    4 4 4

    vkloff
    0.625 0.5 0.25

    The total energy does not converge but it oscillates between two values

    -1527.64676951
    -1530.62775035
    -1526.95854966
    -1531.89151539
    -1526.04966227
    -1531.36819013
    -1527.14213502
    -1530.57037827

    What should I change in my input file to have convergence? I put an high number of empty states as suggested in the Si-HF input file provided in the examples but it does not work.

    Any help would be appreciated.

    Cheers,
    Stefano

     
  • Stefano

    Stefano - 2015-08-15

    It seems to me that the mixing procedure is not implemented for the HF calculation. Is this right?

     
  • supermarche

    supermarche - 2015-08-17

    Dear Stefano,

    NiO might be a metal in HF, and thus is not representable with a single slater determinant. Dirty trick: increase the k-mesh, and the energy difference should get smaller.

    All the best,
    Marc

     
  • Sangeeta Sharma

    Sangeeta Sharma - 2015-08-18

    The calculation as it stands is fine. It takes about 100 iterations to converge. The potential in Hartree-Fock is non-local and it is wavefunction based method mixing something is not a simple task in such a situation.

     
  • Sangeeta Sharma

    Sangeeta Sharma - 2015-08-18

    NiO is not metallic in Hartree-Fock. My preliminary calculations show it to be insulator. Most materials with even number of electrons in a unit-cell are insulating in single particle theories. NiO is one such material. However, it is insulating for wrong reasons.

     

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