[QE-users] unreasonable Ir slab structure yielded after relax

[Tamas Karpati]

Dear Yike Huang,

I guess the problem comes from an inappropriate electronic structure.
First, your system cannot be in a singlet electronic state. Second, the
ground state might be different from the doublet state (even number due to
the odd no. of electrons).

Both can be solved using a senseful value for starting_magnetization
(eg. 1, 3 or so). If still not correct, try a greater value and let QE converge
to the ground state. Consider whether the default value for nspin is
OK for you or not.

Hope this helps,
  Tamas

PS: You may see a surprising no. of alpha and beta electrons near the
beginning of your output file (that you obtained via your enclosed input file).

On Tue, Sep 8, 2020 at 11:30 AM <ykhuang at dicp.ac.cn> wrote:
>
> Greetings, QE users and experts,
>
> I try to relax a seven-layer Ir slab  at gamma point with 15 Angstrom high vacuum added along z-axis, bottom four layers are fixed and top three layers are allowed to relax. However, after relaxation, I find top two layers almost depart from the bottom five layers. Is there something wrong with my input script? I also perform the same calculation on other elements such as Au, Pt and Pd, but problem only emerges in Ir-system.
>
> I attach my input script in the following, any suggestions will be appreciated.
>
> -----------------------------------
>
> &CONTROL
> calculation = 'relax'
> outdir = './Ir7_slab_relax_spin_polarized/'
> prefix = 'opt'
> pseudo_dir = './'
> restart_mode = 'from_scratch'
> tprnfor = .TRUE.
> wf_collect = .TRUE.
> /
>
>
> &SYSTEM
> degauss = 0.002
> ecutwfc = 60
>
> ecutrho = 600
> ibrav = 0
> nat = 7
> ntyp = 1
> occupations = 'smearing'
> /
>
>
> &ELECTRONS
> electron_maxstep = 100
> mixing_beta = 0.5
> scf_must_converge = .TRUE.
> /
>
>
> ATOMIC_SPECIES
> Ir 192.22 Ir_pbe_v1.2.uspp.F.UPF
>
>
> K_POINTS {GAMMA}
>
>
> CELL_PARAMETERS {angstrom}
> 2.7351000000 0.0000000000 0.0000000000
> -1.3675500000 2.3686660819 0.0000000000
> 0.0000000000 0.0000000000 28.3994000000
>
>
> ATOMIC_POSITIONS {angstrom}
> Ir 0 0 0 0 0 0
> Ir 1.3675636755 0.789547465077 2.233328816 0 0 0
> Ir -1.36754999994e-05 1.57911861681 4.466373638 0 0 0
> Ir 0 0 6.699702454 0 0 0
> Ir 1.3675636755 0.789547465077 8.93303127
> Ir -1.36754999994e-05 1.57911861681 11.166076092
> Ir 0 0 13.399404908
>
>
>
> ________________________________
>
> Yike Huang, PhD candidate.
>
> Dalian Institute of Chemical Physics, CAS, China.
>
> _______________________________________________
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