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 <[email protected]> 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%[email protected]>[email protected] > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > -- PRASENJIT GHOSH, IISER Pune, Dr. Homi Bhabha Road, Pashan Pune, Maharashtra 411008, India Phone: +91 (20) 2590 8203 Fax: +91 (20) 2589 9790
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