Dear Dr. Lurii, Thank you for your important suggestions. I have started HP code and got some errors which I have posted in a separate email. I am looking into more details and will get back to you with some updates.
Regards Bhamu On Mon, Nov 15, 2021 at 9:55 PM Iurii TIMROV via users < users@lists.quantum-espresso.org> wrote: > Dear K C Bhamu, > > > > Do you think my input file (see below) has any issues? I have defined > all tetra-Fe sites dn-spin and all octahedra Fe sites up-spin. > > > I recommend to check with the QE input generator: > https://www.materialscloud.org/work/tools/qeinputgenerator > > > > What other things I should take care of to reproduce the band gap (0.14 > eV to 0.3 eV)? > > > I never studied this system but I can give general comments: > > - you can try to determine Hubbard parameters using the HP code of QE > > - you can try to use "ortho-atomic" Hubbard projectors instead of "atomic" > (U_projection_type): https://www.mdpi.com/2076-3417/11/5/2395 > > - maybe try DFT+U+V? > https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.5.104402 > (see Fig. 6) Tutorial: https://www.youtube.com/watch?v=WSABAqPWNH0&t=5s > > > > In the research paper [3] > <https://iopscience.iop.org/article/10.1088/1468-6996/15/4/044202>, the > authors used VASP and the valence configuration for the Fe atom was taken > as 3d64s1. I could not find any PP from the list I mention below which has > this configuration. Does this may be an issue? If anyone has PP of Fe > with 3d64s1 configuration, please provide me. > > > Check SSSP: https://www.materialscloud.org/discover/sssp/table/efficiency > > > HTH > > > Iurii > > > -- > Dr. Iurii TIMROV > Senior Research Scientist > Theory and Simulation of Materials (THEOS) > Swiss Federal Institute of Technology Lausanne (EPFL) > CH-1015 Lausanne, Switzerland > +41 21 69 34 881 > http://people.epfl.ch/265334 > ------------------------------ > *From:* users <users-boun...@lists.quantum-espresso.org> on behalf of Dr. > K. C. Bhamu <kcbham...@gmail.com> > *Sent:* Monday, November 15, 2021 11:47:16 AM > *To:* Quantum Espresso users Forum > *Subject:* [QE-users] Need some suggestion regarding the band gap issue > of Fe3O4 > > Dear QE Users, > > This email may be large for you all as I am trying to put all the > information so that I do not miss any information in your response. > I sincerely apologize for this long email. > > > I am dealing with ferrimagnetic Fe3O4 (with QE6.6) and trying to > reproduce its band gap. In the literature, its experimental band gap was > reported to be in the range of 0.14-0.3eV, Table SI-1 [1] > <https://aip.scitation.org/doi/10.1063/1.5138941> for the up-spin state. > For Fe3O4 nanoparticles, the band gap is reported ~2eV. > > I have tried with all available PPs (mentioned below in different sets) > and U values from 1eV to 7eV. At lower U (=1-2eV), I am getting this > system a direct band-gap half-metal (a gap is opened in the spin-up > channel) and with increasing the U value, the direct band-gap (=~1eV) > nature changes to the indirect (=~2eV) band gap. At U=7eV with the rrkjus > PPs, it showed a metallic character. > > I have also carried out the band structure, by keeping the lattice > parameters fixed at experimental values and only relaxing ionic position, > with varying U-values. But still, the nature of the bang-gap is similar > to what I just mentioned above(band gap varies from ~1eV to ~2eV with > U=1eV to 7eV, respectively). > > The lattice parameters, magnetic moments, and the charge on Fe_tet and > Fe_oct sites I am getting reasonably in accordance with the Table SI-1 > <https://aip.scitation.org/doi/10.1063/1.5138941>. > > A sample of my input file is also shown below (the only PPs are different > with respective cutoffs). > > Information collected from other research papers: > 1. See [2] > <https://www.sciencedirect.com/science/article/abs/pii/S0039602812000544> > (In section 3.1. Bulk Fe3O4: 0.33 eV band gap with VASP with U=3.8eV ). > 2. See [3] > <https://iopscience.iop.org/article/10.1088/1468-6996/15/4/044202> (Page-4, > bottom left para: 2.1 eV using VASP with U=4 eV). This paper only shows > the direct band-gap of 2.1eV. > Based on my already finished calculations and the details that I have > covered above, I have a few queries: > > 1. Do you think my input file (see below) has any issues? I have > defined all tetra-Fe sites dn-spin and all octahedra Fe sites up-spin. > 2. What other things I should take care of to reproduce the band gap > (0.14 eV to 0.3 eV)? > 3. In the research paper [3] > <https://iopscience.iop.org/article/10.1088/1468-6996/15/4/044202>, > the authors used VASP and the valence configuration for the Fe atom was > taken as 3d64s1. I could not find any PP from the list I mention below > which has this configuration. Does this may be an issue? If anyone has > PP of Fe with 3d64s1 configuration, please provide me. > 4. As mentioned in the research paper [4] > <https://pubs.acs.org/doi/full/10.1021/acs.jpcc.7b09387>, the authors > have mentioned that "Our results show that, upon releasing the > symmetry constraint on the density but not on the geometry, charge > disproportionation (Fe2+/Fe3+) is observed, resulting in a band gap of > around 0.2 eV at the Fermi level." How can I release symmetry > constrain on the density? I used nonsym=True also but the calculation was > not converging in this case. > > Supporting information for this email: > > > *Combinations of my PPs:* > > Set-1 (ecutwfc/ecutrho = 40/320Ry) > Fe.pbe-nd-rrkjus.UPF > O.pbe-rrkjus.UPF > > Set-2 (ecutwfc/ecutrho = 45/450Ry) > Fe.pbe-sp-van_mit.UPF > O.pbe-rrkjus.UPF > > *Set-3 (ecutwfc/ecutrho = 65/785Ry) >> similar to yours* > > *Fe.pbe-spn-rrkjus_psl.1.0.0.UPF O.pbe-n-rrkjus_psl.1.0.0.UPF* > > set-4 (ecutwfc/ecutrho = 64/782Ry) > Fe.pbe-spn-kjpaw_psl.0.2.1.UPF > O.pbe-n-kjpaw_psl.0.1.UPF > > *QE input file:* > > &CONTROL > calculation = 'scf' > etot_conv_thr = 1.0000000000d-04 > forc_conv_thr = 1.0000000000d-03 > ! disk_io = 'none' > outdir = './tmp/' > prefix = 'pwscf' > pseudo_dir = '~/PPs/' > ! tprnfor = .true. > ! tstress = .true. > ! verbosity = 'high' > / > &SYSTEM > degauss = 0.01 > ecutrho = 785 > ecutwfc = 65 > ibrav = 0 > nat = 56 > nosym = .false. !! I have tried with .True. also but my calculations > were not converging. > ntyp = 3 > occupations = 'smearing' , smearing = 'mp' > starting_magnetization(1) = 1 > starting_magnetization(2) = -1 > nspin = 2 > lda_plus_u=.true. > Hubbard_U(1)=X (tried 1eV to 7eV) > Hubbard_U(2)=X (tried 1eV to 7eV) > > > / > &ELECTRONS > conv_thr = 1.000000000d-6 > electron_maxstep = 200 > mixing_beta = 3.0000000000d-01 > / > &IONS > ion_dynamics = 'bfgs' > / > &CELL > / > > ATOMIC_SPECIES > Fe1 55.845 Fe.pbe-spn-rrkjus_psl.1.0.0.UPF > Fe2 55.845 Fe.pbe-spn-rrkjus_psl.1.0.0.UPF > O 15.9994 O.pbe-n-rrkjus_psl.1.0.0.UPF > ATOMIC_POSITIONS crystal > Fe1 0.6250000000 0.6250000000 0.6250000000 > Fe1 0.6250000000 0.3750000000 0.3750000000 > Fe1 0.3750000000 0.6250000000 0.3750000000 > Fe1 0.3750000000 0.3750000000 0.6250000000 > Fe1 0.6250000000 0.8750000000 0.8750000000 > Fe1 0.8750000000 0.6250000000 0.8750000000 > Fe1 0.8750000000 0.8750000000 0.6250000000 > Fe1 0.6250000000 0.1250000000 0.1250000000 > Fe1 0.1250000000 0.6250000000 0.1250000000 > Fe1 0.1250000000 0.1250000000 0.6250000000 > Fe1 0.1250000000 0.3750000000 0.8750000000 > Fe1 0.1250000000 0.8750000000 0.3750000000 > Fe1 0.3750000000 0.1250000000 0.8750000000 > Fe1 0.8750000000 0.1250000000 0.3750000000 > Fe1 0.3750000000 0.8750000000 0.1250000000 > Fe1 0.8750000000 0.3750000000 0.1250000000 > Fe2 0.0000000000 0.0000000000 0.0000000000 > Fe2 0.2500000000 0.2500000000 0.2500000000 > Fe2 0.0000000000 0.5000000000 0.5000000000 > Fe2 0.5000000000 0.0000000000 0.5000000000 > Fe2 0.5000000000 0.5000000000 0.0000000000 > Fe2 0.2500000000 0.7500000000 0.7500000000 > Fe2 0.7500000000 0.2500000000 0.7500000000 > Fe2 0.7500000000 0.7500000000 0.2500000000 > O 0.3750000000 0.3750000000 0.3750000000 > O 0.3750000000 0.6250000000 0.6250000000 > O 0.6250000000 0.3750000000 0.6250000000 > O 0.6250000000 0.6250000000 0.3750000000 > O 0.8750000000 0.8750000000 0.8750000000 > O 0.8750000000 0.6250000000 0.6250000000 > O 0.6250000000 0.8750000000 0.6250000000 > O 0.6250000000 0.6250000000 0.8750000000 > O 0.3750000000 0.8750000000 0.8750000000 > O 0.8750000000 0.3750000000 0.8750000000 > O 0.8750000000 0.8750000000 0.3750000000 > O 0.3750000000 0.1250000000 0.1250000000 > O 0.8750000000 0.6250000000 0.1250000000 > O 0.8750000000 0.1250000000 0.6250000000 > O 0.6250000000 0.8750000000 0.1250000000 > O 0.1250000000 0.3750000000 0.1250000000 > O 0.1250000000 0.8750000000 0.6250000000 > O 0.6250000000 0.1250000000 0.8750000000 > O 0.1250000000 0.6250000000 0.8750000000 > O 0.1250000000 0.1250000000 0.3750000000 > O 0.8750000000 0.3750000000 0.3750000000 > O 0.3750000000 0.8750000000 0.3750000000 > O 0.3750000000 0.3750000000 0.8750000000 > O 0.8750000000 0.1250000000 0.1250000000 > O 0.3750000000 0.6250000000 0.1250000000 > O 0.3750000000 0.1250000000 0.6250000000 > O 0.6250000000 0.3750000000 0.1250000000 > O 0.1250000000 0.8750000000 0.1250000000 > O 0.1250000000 0.3750000000 0.6250000000 > O 0.6250000000 0.1250000000 0.3750000000 > O 0.1250000000 0.6250000000 0.3750000000 > O 0.1250000000 0.1250000000 0.8750000000 > K_POINTS automatic > 3 3 3 0 0 0 > CELL_PARAMETERS angstrom > 8.3840000000 0.0000000000 0.0000000000 > 0.0000000000 8.3840000000 0.0000000000 > 0.0000000000 0.0000000000 8.3840000000 > > > > Thank you very much for having patience while going through this detailed > email. > > I look forward to hearing from you. > > > Regards > > K C Bhamu > Postdoctoral Fellow > School of Chemical Engineering > University of Ulsan > South Korea > > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users