[QE-users] zincblende structure, SCF convergence

[Lorenzo Paulatto]

On 09/10/2018 11:52, Michal Krompiec wrote:
> Hello,
> I'm struggling with SCF convergence of something that should be a simple 
> calculation: InP (zincblende structure taken from a CIF). I tried 
> ultra-soft pseudopotentials, PAW, changing the k-point grid, increasing 
> ecutwfc and ecutrho, decreasing mixing_beta and every time the SCF 
> energy is oscillating instead of converging. I would be grateful for any 
> advice.

Hello, are you sure you system does not turn out to be metallic? That 
would make convergence problematic.

Try this the following input (I have removed all input variables that 
you MUST NOT use, unless you really know what you are doing). If it 
works remember to check convergence with ecutwfc/wcutrho (your values 
look very high to me) and of the k-points w.r.t. the degauss value.

cheers

&CONTROL
    calculation = "scf",
    pseudo_dir  = ".",
    outdir      = ".",
    prefix      = "InP",
    verbosity='high'
    restart_mode = "from_scratch"
/
&SYSTEM
    ibrav       = 2,
    nat         = 2,
    ntyp        = 2,
    ecutwfc     = 80,
    ecutrho = 800,
    occupations = "smearing",
      smearing="mv"
      degauss=0.02
    A=5.8687,


/
&ELECTRONS
   mixing_beta=0.2,
   mixing_mode="plain"
/


ATOMIC_SPECIES
In 49 In.pbe-dn-kjpaw_psl.1.0.0.UPF
P 15 P.pbe-n-kjpaw_psl.1.0.0.UPF

ATOMIC_POSITIONS {alat}
In   0.00000   0.00000   0.00000
  P   0.25 0.25 0.25

K_POINTS {automatic}
  9 9 9 0 0 0
> 
> Thanks in advance,
> 
> Michal
> 
> 
> *Dr. Michal Krompiec*
> 
> Adjunct Professor
> 
> School of Chemistry, University of Southampton
> 
> Highfield, Southampton SO17 1BJ, UK
> 
> 
> and
> 
> Head of Computational Modelling | Performance Materials | Early Research 
> and Business Development
> 
> Merck
> 
> 
> 
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-- 
Lorenzo Paulatto - Paris