[Pw_forum] "charge is wrong" error in semiconductor slab calculation

[Eyvaz Isaev]

Hi, 

I will try to repeat my own reply as it was sent only to the first address. That seems to be quite strange, because I used "Reply".

>     ibrav = 8,
>     a = 3.92232131524178,
>     b = 3.92232131524178,
>     c = 22.207375,

Why you use orthorhombic lattice instead of simple tetragonal (ibrav=6) as a=b?

This problem was discussed before many times (you could search in the forum archive):
Most likely you have a metallic system though you claim that you have a semiconducting slab.
So, you should include "occupations" and related keywords, otherwise you have a semiconducting system that causes the charge deficiency due to insufficient bands number.

By the way your system might be metallic due to induced states in the band gap as you consider a slab with surfaces.

Please, provide your affiliation, too.

-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Condensed Matter Theory Group, Uppsala University, Sweden 
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Tue, 12/2/08, J. J. Ramsey <jjr19 at uakron.edu> wrote:

> From: J. J. Ramsey <jjr19 at uakron.edu>
> Subject: [Pw_forum] "charge is wrong" error in semiconductor slab calculation
> To: pw_forum at pwscf.org
> Date: Tuesday, December 2, 2008, 6:36 PM
> I'm doing a slab calculation somewhat similar to that in
> Phys. Rev. B 77, 165323 (2008), except that (1) the geometry
> is simplified down to 10 atoms and (2) the goal is to relax
> the positions of the pseudohydrogens used to passivate the
> bottom of the slab while keeping all other atoms fixed.
> It's partly a dummy problem to shake out the kinks in
> doing a simulation in Quantum Espresso. Here is the input
> file:
> 
> &CONTROL
>     title = "Finding positions of
> pseudohydrogens",
>     calculation= "relax",
>     prefix = findPseudoInitPos_PWscf,
>     pseudo_dir = "Pseudopotentials/"
> /
> &SYSTEM
>     ibrav = 8,
>     a = 3.92232131524178,
>     b = 3.92232131524178,
>     c = 22.207375,
>     nat = 10,
>     ntyp = 4,
>     ecutwfc = 40
> /
> &ELECTRONS
>     conv_thr = 1D-6
> /
> &IONS
>     bfgs_ndim         = 3,
>     pot_extrapolation = "second_order",
>     wfc_extrapolation = "second_order",
> /
> ATOMIC_SPECIES
> Ga 69.723 Ga.pz-bhs.UPF
> In 114.818 In.pz-n-bhs.UPF
> As 74.92160 As.pz-bhs.UPF 
> H* 1.25 01_25-H-tm.fhi.UPF
> ATOMIC_POSITIONS angstrom
> H* 0 0.980580328810445 0 1 1 1
> H* 0 2.94174098643133 0 1 1 1
> Ga 0 0 0.693375 0 0 0
> As 1.96116065762089 0 2.080125 0 0 0
> Ga 1.96116065762089 1.96116065762089 3.466875 0 0 0
> As 0 1.96116065762089 4.853625 0 0 0
> In 0 0 6.240375 0 0 0
> As 1.96116065762089 0 7.732125 0 0 0
> In 1.96116065762089 1.96116065762089 9.223875 0 0 0
> As 0 1.96116065762089 10.715625 0 0 0
> K_POINTS automatic
> 4 4 1 1 1 1
> 
> The error that I get is
> WARNING: integrated charge=    34.15000000, expected=   
> 34.50000000
> 
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>      from electrons : error #         1
>      charge is wrong
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
>      stopping ...
> 
> This happened at the first iteration.
> 
> The pseudopotentials for Ga, In, and As are from the
> pseudopotential tables, and I tested them by using them to
> find the lattice constants of GaAs and InAs, which were
> found to be about 5.547 and 5.967 angstroms, respectively,
> which appears reasonable. The pseudopotential for
> pseudohydrogen was generated from fhi98pp from this input
> file,
> 
>  1.25  0  1  3  0.00 : z  nc  nv iexc rnlc 
>     1  0   1.25      : n  l   f 
> 0  t                 : lmax  s_pp_def 
> 0  0.00  0.00  t     : lt  rct  et  s_pp_type
> 
> and converted to UPF with the fhi2upf utility.
> 
> Input, output, and pseudopotential for pseudohydrogen are
> attached in the job-stuff.tgz tarball.
> 
> Any ideas as to what's wrong?
> 
> 
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