[QE-users] Why does the dipole correction fail?

[Giovanni Cantele]

Because the potential step should be as far as possible from the atoms I
would fix emaxpos as follows: you positions, along edir=3, range (in
crystal units)
from ~0.3 to ~0.6, spanning a ~0.3 interval. That means that the vacuum is
~0.7, the potential step should be in the middle of it, even approximately.
So emaxpos = 0.6 + 0.35 = 0.95 (in this way the potential step will have
the same distance from both sides of the slab).
Another issue that can give you wrong results is that the potential step
should take place in a region with size << axis size along edir=3. So, I
would use foe eopreg a value ten times smaller than yours. Finally, eamp=0
(you do not need a superimpose external field), even though the value you
use shouldn't be the source of problems.
Try to make these changes and see if it works.

By the way, I understand that your input is just for testing purposes. If
not, beware: you're using only one atomic species and two atoms among those
listed in the file.

Giovanni
-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it <giovanni.cantele at spin.cnr.it>
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: https://sites.google.com/view/giovanni-cantele/home


Il giorno mer 16 ott 2024 alle ore 10:54 宋克楠 <songkn at bgi-graphene.com> ha
scritto:

> Dear All,
>
> I am doing the dipole correction to my slab system, where the dipole is
> added along the z axis.
>
> This is my input file in the SCF calculation step.
> &CONTROL
>   title = 'Graphene_SiO2',
>   calculation = 'scf',
>   restart_mode = 'from_scratch',
>   tefield = .true.,
>   dipfield = .true.,
>   pseudo_dir = './'
> /
> &SYSTEM
>   ibrav = 0,
>   nat = 2,
>   ntyp = 1,
>   ecutwfc = 50,
>   ecutrho = 200,
>   nosym = .true.,
>   noinv = .true.,
>   noncolin =.true.,
>   lspinorb=.true.,
>   edir = 3,
>   eopreg = 0.2,
>   emaxpos = 0.8,
>   eamp = 0.001,
>   nbnd = 50,
>   occupations = 'smearing',
>   degauss = 1d-9,
>   vdw_corr = DFT-D3,
>   smearing = 'gaussian'
> /
> &ELECTRONS
>   electron_maxstep = 100,
>   conv_thr = 1.0d-9,
>   mixing_mode = 'plain',
>   mixing_beta = 0.8d0,
>   diagonalization = 'david'
> /
> &IONS
>     ion_positions = 'from_input'
> /
> &CELL
>     cell_dynamics = 'none'
> /
> ATOMIC_SPECIES
>   Si  14.0 Si_ONCV_PBE_fr.upf
>   O   8.0 O_ONCV_PBE_fr.upf
>   C  12.0 C_ONCV_PBE_fr.upf
> CELL_PARAMETERS (angstrom)
>   4.9130001068 0.0000000000  0.0000000000
> -2.4565000534 4.2547829013  0.0000000000
>   0.0000000000 0.0000000000 27.7607002258
> ATOMIC_POSITIONS (crystal)
> Si  0.52990000      0.52990000     0.48013653
> Si  0.00000000      0.47010000     0.41523428
> Si  0.47010000      0.00000000     0.35033203
> O   0.85400000      0.58640000     0.45692101
> O   0.26760000      0.41360000     0.43844982
> O   0.14600000      0.73240000     0.37354756
> O   0.73240000      0.14600000     0.39201875
> O   0.58640000      0.85400000     0.30864531
> O   0.41360000      0.26760000     0.32711649
> C   0.52990000      0.02990000     0.58820290
> C   0.69656667      0.36323333     0.58820290
> C   0.52990000      0.52990000     0.58820290
> C   0.69656667      0.86323333     0.58820290
> C   0.02990000      0.02990000     0.58820290
> C   0.19656667      0.36323333     0.58820290
> C   0.02990000      0.52990000     0.58820290
> C   0.19656667      0.86323333     0.58820290
> K_POINTS automatic
> 15 15 1 1 1 1
>
> This is my input file in the pp.x calculation step.
> &INPUTPP
> prefix = 'pwscf',
> outdir = './',
> plot_num = 11,
> /
> &PLOT
> fileout = 'dipole.dat',
> /
>
> This is my input file in the average.x calculation step.
> 1
> tmp.pp
> 1.0
> 3000
> 3
> 3.0
>
> Then I obtain the avg.dat file. When I plot the dipole, I see no
> correction to the system at all.
> Would anyone please give me some suggestions on how to apply the correct
> the dipole to the system?
>
> Thank you in advance.
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