[QE-users] Need some suggestion regarding the band gap issue of Fe3O4
Dr. K. C. Bhamu
kcbhamu85 at gmail.com
Tue Nov 16 06:09:11 CET 2021
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 at 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-bounces at lists.quantum-espresso.org> on behalf of Dr.
> K. C. Bhamu <kcbhamu85 at 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
>
>
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