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

[ykhuang at dicp.ac.cn]

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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