[Pw_forum] Problem in SCF convergence with larger unit cells
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Sat Jun 11 23:21:46 CEST 2016
Dear Reza Vatan
> ecutwfc = 12.0,
> Ga 69.72 Ga.blyp-d-hgh.UPF
> P 30.97 P.blyp-hgh.UPF
It is very strange that you converge at all with a so minimal cutoff
and so hard hgh norm-conserving pseudopotentials. I would bet that
ecutwfc = 100.0 is barely sufficient for Ga with semicore d shell in
valence. I suggest that you raise ecutwfc and find convergence for GaP
in the 2 atoms cell.
HTH
Giuseppe
Quoting reza vatan <rezavatan64 at gmail.com>:
> Dear all,
>
> I'm trying to optimize the atomic structure of GaP using QE. When I use a
> unit cell only containing two atoms, I have no problem in SCF convergence
> and the structure get optimized in the first step. But when I make my unit
> cell bigger (let's say a unit cell with 64 atoms) just by repeating my
> smaller optimized unit cell in real space and run relax calculation, the
> SCF calculation never get converged. Does anyone know where the problem is?
>
> Following is my input:
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> &CONTROL
> calculation = "relax",
> dt = 30.D0,
> prefix = 'gap',
> pseudo_dir = './',
> outdir='./',
> /
> &system
> ibrav= 6, celldm(1) =20.52, celldm(3) =1, nat= 64, ntyp= 2,
> ecutwfc = 12.0,
> degauss = 0.05D0,
> occupations = "fixed",
> smearing = "methfessel-paxton",
> /
> &ELECTRONS
> conv_thr = 1.D-7,
> mixing_beta = 0.3D0,
> electron_maxstep= 200,
> /
> &IONS
> pot_extrapolation = "second_order",
> wfc_extrapolation = "second_order",
> /
> ATOMIC_SPECIES
> Ga 69.72 Ga.blyp-d-hgh.UPF
> P 30.97 P.blyp-hgh.UPF
> ATOMIC_POSITIONS (angstrom)
> Ga 2.7146780000 2.7146780000 0.0000000000
> Ga 0.0000000000 0.0000000000 0.0000000000
> Ga 2.7146780000 0.0000000000 2.7146780000
> Ga 0.0000000000 2.7146780000 2.7146780000
> P 4.0720170000 4.0720170000 1.3573390000
> P 1.3573390000 1.3573390000 1.3573390000
> P 4.0720170000 1.3573390000 4.0720170000
> P 1.3573390000 4.0720170000 4.0720170000
> Ga 2.7146780000 2.7146780000 5.4293560000
> Ga 0.0000000000 0.0000000000 5.4293560000
> Ga 2.7146780000 0.0000000000 8.1440340000
> Ga 0.0000000000 2.7146780000 8.1440340000
> P 4.0720170000 4.0720170000 6.7866950000
> P 1.3573390000 1.3573390000 6.7866950000
> P 4.0720170000 1.3573390000 9.5013730000
> P 1.3573390000 4.0720170000 9.5013730000
> Ga 2.7146780000 8.1440340000 0.0000000000
> Ga 0.0000000000 5.4293560000 0.0000000000
> Ga 2.7146780000 5.4293560000 2.7146780000
> Ga 0.0000000000 8.1440340000 2.7146780000
> P 4.0720170000 9.5013730000 1.3573390000
> P 1.3573390000 6.7866950000 1.3573390000
> P 4.0720170000 6.7866950000 4.0720170000
> P 1.3573390000 9.5013730000 4.0720170000
> Ga 2.7146780000 8.1440340000 5.4293560000
> Ga 0.0000000000 5.4293560000 5.4293560000
> Ga 2.7146780000 5.4293560000 8.1440340000
> Ga 0.0000000000 8.1440340000 8.1440340000
> P 4.0720170000 9.5013730000 6.7866950000
> P 1.3573390000 6.7866950000 6.7866950000
> P 4.0720170000 6.7866950000 9.5013730000
> P 1.3573390000 9.5013730000 9.5013730000
> Ga 8.1440340000 2.7146780000 0.0000000000
> Ga 5.4293560000 0.0000000000 0.0000000000
> Ga 8.1440340000 0.0000000000 2.7146780000
> Ga 5.4293560000 2.7146780000 2.7146780000
> P 9.5013730000 4.0720170000 1.3573390000
> P 6.7866950000 1.3573390000 1.3573390000
> P 9.5013730000 1.3573390000 4.0720170000
> P 6.7866950000 4.0720170000 4.0720170000
> Ga 8.1440340000 2.7146780000 5.4293560000
> Ga 5.4293560000 0.0000000000 5.4293560000
> Ga 8.1440340000 0.0000000000 8.1440340000
> Ga 5.4293560000 2.7146780000 8.1440340000
> P 9.5013730000 4.0720170000 6.7866950000
> P 6.7866950000 1.3573390000 6.7866950000
> P 9.5013730000 1.3573390000 9.5013730000
> P 6.7866950000 4.0720170000 9.5013730000
> Ga 8.1440340000 8.1440340000 0.0000000000
> Ga 5.4293560000 5.4293560000 0.0000000000
> Ga 8.1440340000 5.4293560000 2.7146780000
> Ga 5.4293560000 8.1440340000 2.7146780000
> P 9.5013730000 9.5013730000 1.3573390000
> P 6.7866950000 6.7866950000 1.3573390000
> P 9.5013730000 6.7866950000 4.0720170000
> P 6.7866950000 9.5013730000 4.0720170000
> Ga 8.1440340000 8.1440340000 5.4293560000
> Ga 5.4293560000 5.4293560000 5.4293560000
> Ga 8.1440340000 5.4293560000 8.1440340000
> Ga 5.4293560000 8.1440340000 8.1440340000
> P 9.5013730000 9.5013730000 6.7866950000
> P 6.7866950000 6.7866950000 6.7866950000
> P 9.5013730000 6.7866950000 9.5013730000
> P 6.7866950000 9.5013730000 9.5013730000
> K_POINTS {automatic}
> 2 2 2 0 0 0
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> Thanks in advance.
>
> Regards,
> Reza Vatan
> School of Electrical, Computer and Energy Engineering
> Arizona State University
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Giuseppe Mattioli
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