[Pw_forum] Graphene_fixed calculation

[Higuchi Toshiharu]

Dear Dr. Seitsonen,

Thank you very much for your kindness reply.
I changed the k points, however the band gap was not 0 eV. 
If you have any comment, please teach me.

k-point(automatic)   HOMO           LUMO           band gap 
40 40 1  1 1 1       -0.8642 eV     -0.6635 eV     0.2007 eV
40 40 1  0 0 0       -0.9682 eV     -0.5618 eV     0.4064 eV
40 40 1  0 0 1       -0.9686 eV     -0.5622 eV     0.4064 eV 

(band gap = LUMO - HOMO)
***********************************************
Dr. Toshiharu Higuchi
University of Tsukuba/ Japan
E-Mail: toshihigu at r7.dion.ne.jp
***********************************************


-----Original Message-----
From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On Behalf Of Ari P Seitsonen
Sent: Tuesday, May 27, 2014 7:08 PM
To: PWSCF Forum
Subject: Re: [Pw_forum] Graphene_fixed calculation


Dear Toshiharu Higuchi,

   How did you determine the band gap? Do you have a k point exactly at the point K of the Brillouin zone? I would guess no, and like I mentioned recently, I do not think that shifting the Monkhorst-Pack k point grid away from the Gamma (or Gamma-bar in two dimensions) point is a good idea.

     Greetings,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   Institut für Chemie der Universität Zürich, CH-8057 Zürich
   Tel: +41 44 63 54 497  /  Mobile: +41 79 71 90 935


On Tue, 27 May 2014, Higuchi Toshiharu wrote:

> 
> Dear Quantum-ESRESSO users,
> 
> I would like to calculate the local density of state of graphene and 
> graphene
> 
> related materials.
> 
> Using the following pw.in file, I calculated the scf under “occupation 
> = fixed”,
> 
> and get the HOMO = -0.8642 eV, and LUMO = -0.6635 eV. This results 
> indicate
> 
> that this graphene is an insulator having a band gap of 0.2007 eV.
> 
> However, this model is half-metal having a band gap of 0.0 eV, if I 
> calculated by
> 
> this process: (1)SCF (smearing) -> nscf (tetrahedra) -> ProjWFC.
> 
> Why will it become the error when I set ‘occupation = fixed’?
> 
> I would really appreciate if you teach me.
> 
> ******************************************************************
> 
> &CONTROL
> 
>                        title = 'Graphene_1A2' ,
> 
>                  calculation = 'scf' ,
> 
>                 restart_mode = 'from_scratch' ,
> 
>                       outdir = '/home/user/tmp/' ,
> 
>                   pseudo_dir = 
> '/home/user/espresso-5.0.1/espresso-5.0.1/pseudo/' ,
> 
>                       prefix = 'Graphene_1A2' ,
> 
>                    verbosity = 'high' ,
> 
> /
> 
> &SYSTEM
> 
>                        ibrav = 4,
> 
>                    celldm(1) = 4.6595,
> 
>                    celldm(3) = 4.0571,
> 
>                          nat = 2,
> 
>                         ntyp = 1,
> 
>                      ecutwfc = 40 ,
> 
>                      ecutrho = 200 ,
> 
>                         nbnd = 150,
> 
>                  occupations = 'fixed' ,
> 
>                      degauss = 0.02 ,
> 
>                     smearing = 'gaussian' ,
> 
>             exxdiv_treatment = 'gygi-baldereschi' ,
> 
> /
> 
> &ELECTRONS
> 
>             electron_maxstep = 100,
> 
>                     conv_thr = 1.D-8 ,
> 
> /
> 
> ATOMIC_SPECIES
> 
>     C   12.01100  C.pz-rrkjus.UPF
> 
> ATOMIC_POSITIONS angstrom
> 
>     C      0.000000000    0.000000000    0.000000000
> 
>     C      1.232850116    0.706423116    0.000000000
> 
> K_POINTS automatic
> 
>   40 40 1   1 1 1
> 
>  
> 
> **********************************************************************
> ****************
> 
> Toshiharu Higuchi
> 
> University of Tsukuba/ Japan
> 
> E-Mail: toshihigu at r7.dion.ne.jp
> 
> **********************************************************************
> ****************
> 
>  
> 
> 
>