[DFTB-Plus-User] DFTB-Plus-User Digest, Vol 99, Issue 31

[Benjamin Hourahine]

Hello Bicai,

Have you tried increasing the electronic temperature? You could also try a different filling function from a Fermi distribution which would have a much lower electronic entropy at high temperatures.

Also, for a metal, the number of k-points is very low and, depending on symmetry, you should shift the grid:

Filling = MethfesselPaxton {
     Temperature [Kelvin] = 1.0e+4
     Order = 2
}
KPointsAndWeights = SupercellFolding {
    10  0 0
    0  10 0
    0 0  10
    0.5 0.5 0.5
}

The U constants are probably not necessary for Fe.

Regards

Ben

       Dr. B. Hourahine, SUPA, Department of Physics,
     University of Strathclyde, John Anderson Building,
             107 Rottenrow, Glasgow G4 0NG, UK.
     +44 141 548 2325, benjamin.hourahine at strath.ac.uk

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________________________________
From: DFTB-Plus-User <dftb-plus-user-bounces at mailman.zfn.uni-bremen.de> on behalf of BiCai Pan via DFTB-Plus-User <dftb-plus-user at mailman.zfn.uni-bremen.de>
Sent: 23 November 2022 01:23
To: dftb-plus-user at mailman.zfn.uni-bremen.de <dftb-plus-user at mailman.zfn.uni-bremen.de>
Cc: BiCai Pan <bcpan at ustc.edu.cn>
Subject: Re: [DFTB-Plus-User] DFTB-Plus-User Digest, Vol 99, Issue 31

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Dear Bálint,

    I am a new user for DFTB. I employed the DFTB to relax a supercell containing 127 Fe atoms, in which there is a vacancy. However, the SCC is not converged even the number of the steps of runing is 200.
    In additoin, I do not know how to add the on-site U term in the input file.
    I do not know what is wrong. Maybe some parameters in the input file are wrong. Can you help me?

Thank you very much!

Best,

Bicai

    In my calculations, the main parameters are below:

        Fe-Fe = "/home/bcpan/DFTB/trans3d-0-1/Fe-Fe.skf"

  MaxSCCIterations = 200
  Solver = DivideAndConquer {}

  KPointsAndWeights = SupercellFolding {
    3  0 0
    0  3 0
    0 0  3
    0.0 0.0 0.0
}

 Filling = Fermi {
    Temperature [K] = 100
  }

  SpinPolarisation = Colinear {
    UnpairedElectrons = 90
    RelaxTotalSpin = Yes
  }

  SpinConstants = {
    Fe = {
      -0.016 -0.012 -0.003 -0.012 -0.029 -0.001 -0.003 -0.001 -0.015
    }
    ShellResolvedSpin = Yes
  }
}
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