[QE-users] zincblende structure, SCF convergence

[Michal Krompiec]

Dear Lorenzo,
Thank you. I am sure the system is not metallic, the band gap (calculated
with PBE) should be around 0.59 eV (vs. experimental 1.41 eV). I tried your
suggestions, but with no luck (energy oscillates instead of converging). I
tried changing mixing_beta from 0.05 to 0.9, increasing and decreasing
number of k-points - still the same.
In the meantime, I did a calculation on exactly the same system in CASTEP
without any problems (default settings, 3x3x3 Monkhorst-Pack grid), with
on-the-fly USPs and also with norm-conserving ones. So clearly I am doing
something wrong or there is something not right with my QE build (6.3,
compiled with Intel 2017 compilers and Intel MPI).
I would be very grateful for any further suggestions.

Best wishes,

Michal


On Tue, 9 Oct 2018 at 10:57, Lorenzo Paulatto <paulatz at gmail.com> wrote:

> 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
> >
> >
> >
> > _______________________________________________
> > users mailing list
> > users at lists.quantum-espresso.org
> > https://lists.quantum-espresso.org/mailman/listinfo/users
> >
>
> --
> Lorenzo Paulatto - Paris
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