[Pw_forum] How to get the usual ~2.4 eV band gap of ZnO with HSE06?

[Prasenjit Ghosh]

Since the hybrid functionals are non ab initio, you can play around with
the % of EXX to see how that affects the band gap (assuming everything else
is fine). Or else you can use GGA+U with U on both Zn and O to correct the
band gap as has been shown in the following paper

J. Phys. Chem. C, * 119 *, 3060 (2015)

and J. Am. Chem. Soc. *133, *5893 (2011).

With regards,

Prasenjit

On 8 August 2017 at 14:54, Tan Hengxin <tanhx90 at gmail.com> wrote:

> Dear all,
>
> I am doing some calculations on the HSE06 (25% EXX) band gap of wurtzite
> ZnO with experimental structure, and find that I cannot get the usual value
> of ~2.4 eV. My value is just ~2.1 eV.
> Maybe my norm-conserving pseudopotentials (NC-PPs) of Zn and O are not
> very good. So I also tried the NC-PPs for Zn and O from the
> pslibrary.0.3.1. However, the gap is even smaller (~1.8 eV). (All PPs are
> based on PBE xc.)
> I have also done different tests with different parameters, containing
> nbnd, nqx1, nqx2, nqx3, k-mesh. But I still cannot get 2.4 eV for the HSE
> gap.
>
> So could anyone provide a guidance on how to obtain the usual HSE band gap
> of 2.4 eV for wurtzite ZnO ? The input parameters are as follows, and the
> output file calculated with the NC-PPs from the pslibrary.0.3.1 is also
> attached. Thank you in advance!
>
> My input parameters for the scf run:
> &CONTROL
>   calculation   = 'scf',
>   prefix        = 'ZnO',
>   pseudo_dir    = './',
> ! nstep         = 200,
>   verbosity     = 'high',
>   wf_collect    = .true.
>   etot_conv_thr = 1.0D-5,
>   forc_conv_thr = 1.0D-4,
>   restart_mode  = 'from_scratch',
>   outdir        = './temp_out',
> /
> &SYSTEM
>   ibrav         = 0,
> ! celldm(1)     = 1.88972688,
>   nat           = 4,
>   ntyp          = 2,
>   ecutwfc       = 60,
> ! ecutrho       = 240,
> ! nosym         = .true.
>   nbnd          = 36,
> ! occupations   = 'smearing',
> ! degauss       = 0.000367,
> ! smearing      = 'gaussian',
>   input_dft     = 'hse',
>   exx_fraction  = 0.25,
> ! screening_parameter = 0.106
> ! exxdiv_treatment    = gygi-baldereschi
>   nqx1 = 3, nqx2 = 3, nqx3 = 2,
> ! nspin         = 2
> ! starting_magnetization(1) = 1.0,
> ! starting_magnetization(2) = -1.0,
> ! lda_plus_u    = .true.
> ! hubbard_U(5)  = 2.59,
> ! hubbard_alpha(2) = 0.d0,
> ! hubbard_U(2)     = 3,
> /
> &ELECTRONS
> ! electron_maxstep = 100,
>   mixing_mode   = 'plain',
>   mixing_beta   = 0.7,
>   conv_thr      = 1.D-8,
> ! startingwfc   ='atomic+random',
> ! startingpot   ='atomic',
> /
> &IONS
>   ion_dynamics      = 'bfgs',
>   pot_extrapolation = 'atomic',
>   upscale           = 100,
>   trust_radius_ini  = 0.5,
> /
> &CELL
>   cell_dynamics     = 'bfgs',
>   press_conv_thr    = 0.5,
>   cell_dofree       = 'all',
> /
>
> ATOMIC_SPECIES
>  Zn 65.38     Zn.pbe-nc.UPF
>  O  15.999    O.pbe-nc.UPF
>
> CELL_PARAMETERS (angstrom)
>      3.249         0.000         0.000
>     -1.625         2.814         0.000
>      0.000         0.000         5.205
>
> ATOMIC_POSITIONS (crystal)
> Zn    0.333333343         0.666666687         0.000000000
> Zn    0.666666627         0.333333313         0.500000000
> O     0.333333343         0.666666687         0.382600009
> O     0.666666627         0.333333313         0.882600009
>
> K_POINTS {automatic}
>  9 9 6 0 0 0
>
> Regards,
> Hengxin Tan, PhD
> Department of Physics
> Tsinghua University.
> --
>
> Tan Hengxin
> Department of physics, THU.
> Beijing 100084, China
> Office: B403,New Science Building
> E-mail:t <E-mail%3Athx13 at mails.tsinghua.edu.cn>anhx90 at gmail.com
>
>
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-- 
PRASENJIT GHOSH,
IISER Pune,
Dr. Homi Bhabha Road, Pashan
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Phone: +91 (20) 2590 8203
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