[Pw_forum] nqx in HSE

[Amin Torabi]

Dear all,

Using the following input file, I am trying to reproduce the bandgap of ZnS
(wurtzite). The structure is optimized (vc-relax at 1 atm) employing
PBEsol, and now I am using HSE to do scf.

Question:
using nqx1=nqx2=nqx3=1,  I found the bandgap to be 3.66 eV, which is
comparable to others (PRL 102, 226401 (2009); however, by using nqx1=nqx2=3
and nqx3=2, the bandgap is reduced to 3.24ev.

Does denser auxiliary mesh not mean an improved calculation?
I would appreciate any comment on my input file?
Thanks!



&CONTROL
         calculation     = 'scf'
        prefix          = 'ZnS'
        pseudo_dir      = '...'
        outdir          = '...'
/
&SYSTEM
        ibrav            = 0
        celldm(1)      = 7.20174629
        nat               = 4
        ntyp             = 2
        nbnd            = 20
        ecutwfc        = 110
        nqx1            = 1
        nqx2            = 1
        nqx3            = 1
        input_dft       = 'hse'
        x_gamma_extrapolation = .true
        exxdiv_treatment='gygi-baldereschi'
/
&ELECTRONS
        conv_thr        = 1.0D-7
/
ATOMIC_SPECIES
 Zn 65.409  Zn.pbe-nc.UPF
 S  32.066  S.pbe-n-nc.UPF
CELL_PARAMETERS (alat=  7.20174629)
   0.992513482   0.000001434   0.000000000
  -0.496255499   0.859542606   0.000000000
   0.000000000   0.000000000   1.628169588
ATOMIC_POSITIONS (crystal)
Zn       0.333333038   0.666666962   0.000366211
Zn       0.666666962   0.333333038   0.500366148
S        0.333333175   0.666666825   0.374633891
S        0.666666825   0.333333175   0.874633750
K_POINTS automatic
 6 6 4 0 0 0


-- 
***************************************
Amin Torabi
Ph.D. Student
Chemistry Dept.
Western University
London, On Canada, N6A 5B7
Phone: 519-661-2111 Ext: 87871
****************************************
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