[QE-users] charging a defect (spreading of charge)

[Christoph Wolf]

Dear all,

I am currently trying to charge a metallic defect (Fe) on an insulating
host (MgO). I am facing the problem that the excess charge seems to be
spread out in the vacuum (resulting in a "slump" in the the electrostatic
potential located in the middle of the vacuum region) and is very
determined to avoid the Fe.

Is there any method to "motivate" the electron to hop onto the impurity? I
tried to increase the hubbard U (no effect), move the dipfield dipole
further or closer to the slab (no effect), increase the vacuum region
(spreads the charge out more but does not help to localize it either)...
and I am a bit lost; Any hint is greatly appreciated!

Best,
Chris


&control
 calculation = 'relax'
 prefix='mgo',
 pseudo_dir = '../00_pseudo',
 outdir='./'
 wf_collect=.true.
 verbosity='high'
 tefield = .true.
 dipfield =.true.
 nstep = 300
/
&SYSTEM
 ibrav     = 6
 celldm(1) =    16
 celldm(3) =    2 ! 2.5 3.0
 nat       = 65
 ntyp      = 3
 ecutwfc = 100.0,
 occupations = 'smearing'
 smearing = 'm-p'
 degauss = 0.001
 eamp        = 0.00
 edir        = 3
 emaxpos     = 0.65 ! 0.70, 0.80, 0.90
 eopreg      = 0.05
 nspin        = 2
 starting_magnetization(3)=0.7 ! tested -0.7 to 0.7
 lda_plus_u=.true.
 hubbard_u(3)=3.5  !tested 1D-40 to 10
 tot_charge = -1
/
&ELECTRONS
 conv_thr=1e-10
 mixing_mode='local-TF'
 mixing_beta=0.1
 diagonalization='cg'
/
&ions
/
ATOMIC_SPECIES
  Mg   24.30500  Mg_ONCV_PBE.UPF
   O   15.99900  O_ONCV_PBE.UPF
  Fe   55.00000  Fe_ONCV_PBE.UPF
ATOMIC_POSITIONS {bohr}
Mg   0.000000000000000   0.000000000000000   0.000000000000000  0 0 0
 O   3.984487481850000   0.000000000000000   0.000000000000000  0 0 0
Mg   7.968974963700000   0.000000000000000   0.000000000000000  0 0 0
 O  11.953462445550000   0.000000000000000   0.000000000000000  0 0 0
 O   0.000000000000000   3.984487481850000   0.000000000000000  0 0 0
Mg   3.984487481850000   3.984487481850000   0.000000000000000  0 0 0
 O   7.968974963700000   3.984487481850000   0.000000000000000  0 0 0
Mg  11.953462445550000   3.984487481850000   0.000000000000000  0 0 0
Mg   0.000000000000000   7.968974963700000   0.000000000000000  0 0 0
 O   3.984487481850000   7.968974963700000   0.000000000000000  0 0 0
Mg   7.968974963700000   7.968974963700000   0.000000000000000  0 0 0
 O  11.953462445550000   7.968974963700000   0.000000000000000  0 0 0
 O   0.000000000000000  11.953462445550000   0.000000000000000  0 0 0
Mg   3.984487481850000  11.953462445550000   0.000000000000000  0 0 0
 O   7.968974963700000  11.953462445550000   0.000000000000000  0 0 0
Mg  11.953462445550000  11.953462445550000   0.000000000000000  0 0 0
 O   0.000000000000000   0.000000000000000   3.984487481850000
Mg   3.984487481850000   0.000000000000000   3.984487481850000
 O   7.968974963700000   0.000000000000000   3.984487481850000
Mg  11.953462445550000   0.000000000000000   3.984487481850000
Mg   0.000000000000000   3.984487481850000   3.984487481850000
 O   3.984487481850000   3.984487481850000   3.984487481850000
Mg   7.968974963700000   3.984487481850000   3.984487481850000
 O  11.953462445550000   3.984487481850000   3.984487481850000
 O   0.000000000000000   7.968974963700000   3.984487481850000
Mg   3.984487481850000   7.968974963700000   3.984487481850000
 O   7.968974963700000   7.968974963700000   3.984487481850000
Mg  11.953462445550000   7.968974963700000   3.984487481850000
Mg   0.000000000000000  11.953462445550000   3.984487481850000
 O   3.984487481850000  11.953462445550000   3.984487481850000
Mg   7.968974963700000  11.953462445550000   3.984487481850000
 O  11.953462445550000  11.953462445550000   3.984487481850000
Mg   0.000000000000000   0.000000000000000   7.968974963700000
 O   3.984487481850000   0.000000000000000   7.968974963700000
Mg   7.968974963700000   0.000000000000000   7.968974963700000
 O  11.953462445550000   0.000000000000000   7.968974963700000
 O   0.000000000000000   3.984487481850000   7.968974963700000
Mg   3.984487481850000   3.984487481850000   7.968974963700000
 O   7.968974963700000   3.984487481850000   7.968974963700000
Mg  11.953462445550000   3.984487481850000   7.968974963700000
Mg   0.000000000000000   7.968974963700000   7.968974963700000
 O   3.984487481850000   7.968974963700000   7.968974963700000
Mg   7.968974963700000   7.968974963700000   7.968974963700000
 O  11.953462445550000   7.968974963700000   7.968974963700000
 O   0.000000000000000  11.953462445550000   7.968974963700000
Mg   3.984487481850000  11.953462445550000   7.968974963700000
 O   7.968974963700000  11.953462445550000   7.968974963700000
Mg  11.953462445550000  11.953462445550000   7.968974963700000
 O   0.000000000000000   0.000000000000000  11.53462445550000
Mg   3.984487481850000   0.000000000000000  11.953462445550000
 O   7.968974963700000   0.000000000000000  11.953462445550000
Mg  11.953462445550000   0.000000000000000  11.953462445550000
Mg   0.000000000000000   3.984487481850000  11.953462445550000
 O   3.984487481850000   3.984487481850000  11.953462445550000
Mg   7.968974963700000   3.984487481850000  11.953462445550000
 O  11.953462445550000   3.984487481850000  11.953462445550000
 O   0.000000000000000   7.968974963700000  11.953462445550000
Mg   3.984487481850000   7.968974963700000  11.953462445550000
 O   7.968974963700000   7.968974963700000  11.953462445550000
Mg  11.953462445550000   7.968974963700000  11.953462445550000
Mg   0.000000000000000  11.953462445550000  11.953462445550000
 O   3.984487481850000  11.953462445550000  11.953462445550000
Mg   7.968974963700000  11.953462445550000  11.953462445550000
 O  11.953462445550000  11.953462445550000  11.953462445550000
Fe   0.000000000      0.0000000000   17.000000000000
K_POINTS automatic
 3 3 1 0 0 0

-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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