Hi, maybe you should check your reference calculation, pay attention to the used k-point grid, cutoff, lattice constant and so on, because the risk is to compare calculations that are not made under the same conditions.
This being said, the calculation can run quite easily on a PC, so I was able to run it: 1) with the lattice constant you provided, the system is slightly metallic (conduction band and valence band overlap in a tiny energy region) 2) using a more appropriate lattice constant, and relaxing the atomic positions, which I took from this paper https://www.sciencedirect.com/science/article/pii/S0169433224002083 which uses the commercial package you mentioned, I get a very similar band structure (Fig. 3d therein) and and energy gap of 0.64 eV to be compared with 0.59 eV that can be obtained from the band structure plot. The two gaps do not seem to differ so much. I downloaded PAW pseudopotentials from the QE web site. Here the input I used: - geometry optimization &CONTROL calculation='relax' title='naalo2 opt' outdir='./tmp/' prefix='pwscf' pseudo_dir='.' verbosity='high' tprnfor=.true. tstress=.true. etot_conv_thr=1d-14 forc_conv_thr=1d-05 / &SYSTEM ibrav=4 a = 3.32 c = 20 nat=4 ntyp=3 ecutwfc=70 ecutrho=560 assume_isolated='2D' occupations='smearing' smearing='gaussian' degauss=0.005d0 / &ELECTRONS conv_thr=1d-10 diago_full_acc = .true. / &IONS / ATOMIC_SPECIES Na 22.98980000 Na.pbe-spn-kjpaw_psl.1.0.0.UPF Al 26.98150000 Al.pbe-n-kjpaw_psl.1.0.0.UPF O 15.99940000 O.pbe-n-kjpaw_psl.1.0.0.UPF ATOMIC_POSITIONS (crystal) Na 0.00000000000000 0.00000000000000 0.59729949500415 Al 0.66666666666667 0.33333333333333 0.44829871971219 O 0.66666666666667 0.33333333333333 0.53369883039369 O 0.33333333333333 0.66666666666667 0.42070295488990 K_POINTS {automatic} 8 8 1 0 0 0 - nscf for band structure calculation same as above with calculation='bands' and K_POINTS { crystal_b } 4 gG 50 M 50 K 50 gG 50 I would suggest to play with calculation parameters, to make a careful lattice constant optimization, and so on, before trying to obtain from your calculation numberd to be compared with previous works. Giovanni -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected] <[email protected]> Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: https://sites.google.com/view/giovanni-cantele/home Il giorno mer 5 mar 2025 alle ore 20:35 Zahid Rashid via users < [email protected]> ha scritto: > Dear QE users, > > I am trying to calculate the electronic band structure for 2D hexagonal > NaAlO2 monolayers using Quantum Espresso 7.3. The band structure for this > system has already been reported with a commercial package (VASP) and the > band gap (reproducible) is ~ 0.35 eV (direct at Gamma point) using PBE > functional and PAW pseudopotentials. > Using Quantum Espresso-7.3, I tried to reproduce these results using PBE + > PAW, PBEsol + PAW, PBE + Ultrasoft pseudopotentials, PBE + ONCVPSP > (Optimized Norm-Conservinng Vanderbilt pseudopotential), PBE + NC > (Troullier-Martins) PSlibrary 0.3.1 downloaded from > https://theos-wiki.epfl.ch/en/Main/Pseudopotentials . All these > pseudopotentials give a zero band gap. I tried a wave function cutoff value > upto 150 Ry with ecutrho = 4 * ecutwfc . > FHI PP with PBE from QE site gives a band gap of ~ 0.11 eV. > Next I also calculated the band structure using NC PPs and HSE functional > and I get a band gap (~ 1.27 eV) comparable to the reported value of ~1.2 > eV. My input for vc-relax is attached. The lattice constants reported with > commercial package are a = b = 3.19 angstroms. I get a value between ~ 3.16 > to 3.188 angstroms with different pseudopotentials. Can you give some > suggestions to reproduce the band gap with PBE functional for this system > using QE package? > > &CONTROL > calculation='vc-relax', > title='naalo2 opt', > outdir='.', > prefix='pwscf', > pseudo_dir='.', > verbosity='high', > tprnfor=.true., > tstress=.true., > etot_conv_thr=1d-14, > forc_conv_thr=1d-05, > / > > &SYSTEM > ibrav=4, > celldm(1) = 5.9704784375296835 > celldm(3) = 6.330233506939965 > nat=4, > ntyp=3, > ecutwfc=110, > ecutrho=440, > input_dft='pbe', > assume_isolated='2D', > occupations='smearing', > smearing='gaussian', > degauss=0.005d0, > / > > &ELECTRONS > conv_thr=1d-10, > diagonalization='david' > diago_full_acc = .true. > / > > &IONS > ion_dynamics='bfgs', > / > > &CELL > cell_dofree='2Dxy' > cell_dynamics='bfgs', > press=0.0d0, > press_conv_thr=0.1d0, > / > > ATOMIC_SPECIES > Na 22.98980000 Na.pbe-n-nc.UPF > Al 26.98150000 Al.pbe-n-nc.UPF > O 15.99940000 O.pbe-nc.UPF > > ATOMIC_POSITIONS (crystal) > Na 0.00000000000000 0.00000000000000 > 0.59729949500415 > Al 0.66666666666667 0.33333333333333 > 0.44829871971219 > O 0.66666666666667 0.33333333333333 > 0.53369883039369 > O 0.33333333333333 0.66666666666667 > 0.42070295488990 > > K_POINTS {automatic} > 25 25 1 0 0 0 > > Regards. > > Zahid Rashid > Department of Chemistry, > Quaid-i-Azam University, Islamabad, Pakistan. > > > _______________________________________________________________________________ > The Quantum ESPRESSO Foundation stands in solidarity with all civilians > worldwide who are victims of terrorism, military aggression, and > indiscriminate warfare. > > -------------------------------------------------------------------------------- > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________________________________________ The Quantum ESPRESSO Foundation stands in solidarity with all civilians worldwide who are victims of terrorism, military aggression, and indiscriminate warfare. -------------------------------------------------------------------------------- Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
