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Castep .cell file for GaN Zinc-blende

  1. Dec 25, 2015 #1
    1. The problem statement, all variables and given/known data
    We have been asked to make 4 .cell files for castep. 3 of them are fine, but the last one we were asked to convert our .cell files GaN (wurzite structure) to GaN (Zincblende) in an 8x8x8 (8x8x6) mp grid.

    We were given a website to convert the convectional lattice parameters to the primitive cell : http://www.cryst.ehu.es/cryst/celltran.html

    But I really am not sure how to completely go about this.

    2. Relevant equations
    My GaN(wurzite structure) .cell file as I refer to it alot.

    %block lattice_abc
    3.1890 3.1890 5.1850
    90.0000 90.0000 120.0000
    %endblock lattice_abc

    %block positions_frac
    Ga 0.66666667 0.33333333 0.000000
    Ga 0.33333333 0.66666667 0.500000
    N 0.66666667 0.33333333 0.375000
    N 0.33333333 0.66666667 0.875000
    %endblock positions_frac

    kpoints_mp_grid 8 8 8

    %block spectral_kpoints_path
    0.000000 0.0000000 0.5000000 ! A
    0.000000 0.5000000 0.5000000 ! L
    0.000000 0.5000000 0.0000000 ! M
    0.000000 0.0000000 0.0000000 ! Gamma
    0.000000 0.0000000 0.5000000 ! A
    -0.333333 0.6666667 0.5000000 ! H
    -0.333333 0.6666667 0.0000000 ! K
    0.000000 0.0000000 0.0000000 ! Gamma
    %endblock spectral_kpoints_path

    snap_to_symmetry


    symmetry_generate

    3. The attempt at a solution
    What I have at the moment is

    %block lattice_abc
    3.0436 1.5945 3.0436
    74.810 53.960 74.810
    %endblock lattice_abc

    %block positions_frac
    Ga 0.00 0.00 0.00
    N 0.25 0.25 0.25
    %endblock positions_frac

    kpoints_mp_grid 8 8 6

    %block spectral_kpoints_path
    0.5000 0.5000 0.5000 ! L
    0.0000 0.0000 0.0000 ! Gamma
    0.5000 0.0000 0.5000 ! X
    0.5000 0.2500 0.7500 ! W
    0.3750 0.3750 0.7500 ! K
    0.5000 0.5000 0.5000 ! L
    %endblock spectral_kpoints_path

    snap_to_symmetry

    symmetry_generate


    Starting from this base file


    %block lattice_abc
    %endblock lattice_abc

    %block positions_frac
    %endblock positions_frac

    kpoints_mp_grid 8 8 6

    %block spectral_kpoints_path
    %endblock spectral_kpoints_path

    snap_to_symmetry

    symmetry_generate

    GaN (z.b.) is fcc, so the spectral_kpoints_path straightforward as we were given samples in previous weeks.

    After that I'm not sure about the positions_frac, I assumed it would be similar to other fcc structured so I have used the same structure as GaAs.

    The for the lattice_abc I put the GaN (wurz) into the website we were provided and that give the result in the .cell provided.

    This gives a very similar structure to GaAs. Which I think should be good as they're both fcc, but i'm really not sure if what I have done is correct.


    I would be very appreciative of any help.

    Thanks.
     
  2. jcsd
  3. Dec 30, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
     
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