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I want to know how to calculate the band structure and DOS of a thin layer of iron selenide in quantum espresso. How I can fix the input file? Is it different from Bulk matter or the same? Which parameter(s) do I need to will change?

This is my input file
&CONTROL
    calculation = "scf"
    outdir      =  "FeSe"
    pseudo_dir  = "."
/

&SYSTEM
    a                         =  3.93329e+00
    c                         =  5.85659e+00
    degauss                   =  1.00000e-02
    ecutrho                   =  2.25000e+02
    ecutwfc                   =  2.50000e+01
    ibrav                     = 6
    nat                       = 4
    nspin                     = 2
    ntyp                      = 2
    occupations               = "smearing"
    smearing                  = "gaussian"
    starting_magnetization(1) =  2.00000e-01
    starting_magnetization(2) =  0.00000e+00
/

&ELECTRONS
    conv_thr         =  1.00000e-06
    electron_maxstep = 200
    mixing_beta      =  4.00000e-01
    startingpot      = "atomic"
    startingwfc      = "atomic+random"
/

K_POINTS {automatic}
 3  3  2  0 0 0

ATOMIC_SPECIES
Fe   55.84500  Fe.pbe-nd-rrkjus.UPF
Se   78.96000  Se.pbe-n-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS {angstrom}
Fe    1.5   1.966645   0.000000
Fe    0.000000   0.000000   0.000000
Se    1.966645   0.000000   1.50
Se    0.000000   1.966645   4.347667
$\endgroup$
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    $\begingroup$ Please provide your input file. $\endgroup$ May 31, 2023 at 2:52
  • $\begingroup$ The workflow for the band structure/DOS doesn't change depending on your crystal's geometry. Here you can find one way to obtain these properties. If you want a step-by-step guide, follow video no 3.1 to 3.4 of this youtube playlist. $\endgroup$ May 31, 2023 at 21:17
  • $\begingroup$ I follow the video that you share with me. I did that one. But now I want to calculate at a thin layer. Please can you help me how to calculate the thin layer? $\endgroup$ Jun 1, 2023 at 1:28
  • $\begingroup$ @BokaFikaduBanti if you followed that tutorial, then for a thin layer, the procedure remains the same. You have to follow the same steps. The only change you need to make is the geometry of your material, i.e., define the ATOMIC_POSITIONS, ibrav and other geometrical parameters instead of bulk material (alternatively, load it from some CIF file). Check out these examples input files for graphene. There is also monolayer MoS2 and bi-layer graphene examples in the same repo. which might help you understand how to proceed. $\endgroup$ Jun 1, 2023 at 3:41
  • $\begingroup$ Thank you very much for sharing nice information. Please can you help me how to fix my atomic position and number of an atom? $\endgroup$ Jun 1, 2023 at 6:34

1 Answer 1

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I think that you have probably mistakenly taken Quantum ESPRESSO (QE) as a geometry builder tool. You CANNOT construct thin layers or slab surfaces from bulk using QE. QE is a tool to calculate certain properties of different materials. But it cannot build the material geometry itself. You need other codes to build the geometry (or you can try to manually enter it if it's a simple one).

As suggested in the comment, in this answer, this tutorial link has been provided which shows how to construct a thin layer geometry using VESTA. There are also many other tools. For example, using BURAI, you can model any slab surface if you have the QE input file for the bulk (alternatively, you can use a CIF file). It directly generates a QE input file. It can even perform certain (scf, nscf, dos, band structure, relax, vc-relax) QE calculations (in fact it is GUI for QE).

Follow these steps, and if you are stuck at some point, please ask questions on a separate thread specifying what type of problem you are facing such as about the installation problem of any particular program, or suggested workflow for certain goals, etc. Otherwise, the question becomes too vague to answer.

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