[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


-- 
********************************************************
- Article premier - Les hommes naissent et demeurent
libres et égaux en droits. Les distinctions sociales
ne peuvent être fondées que sur l'utilité commune
- Article 2 - Le but de toute association politique
est la conservation des droits naturels et
imprescriptibles de l'homme. Ces droits sont la liberté,
la propriété, la sûreté et la résistance à l'oppression.
********************************************************

    Giuseppe Mattioli
    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
    v. Salaria Km 29,300 - C.P. 10
    I 00015 - Monterotondo Stazione (RM)
    Tel + 39 06 90672836 - Fax +39 06 90672316
    E-mail: <giuseppe.mattioli at ism.cnr.it>
    http://www.ism.cnr.it/en/staff/giuseppe-mattioli/
    ResearcherID: F-6308-2012





More information about the users mailing list