\(\alpha\)-Fe with ferromagnetic calculation

In this example, you will learn how to perform a ferromagnetic DFT+G calculation using Wien2k plus CyGutz packages, including some typical post-analyses.

  1. Finish a self-consistent LDA paramagnetic calculation (run_lapw)

    for \(\alpha\)-Fe (bcc) using Wien2k. Here is the structure file Fe.struct. To compare with the provided results, one should keep the RMT = 2.33 as specified in the Fe.struct, RMT * KMAX = 8.0 and total number of k-points = 5000 (17x17x17). We do not shift k-points here. In the end, check the total LDA energy in the Fe.scf file, which should be close to -2541.12378 Ryd.

  2. Use the following command to initialize the Gutzwiller calculation,

    Type:

    $ ${WIEN_GUTZ_ROOT2}/init_ga.py

    Answer the questions as follows:

    • Do you want to BREAK SPIN-SYMMETRY: y
    • Do you want to COMPLETELY break orbital-symmetry: n
    • Do you want to take into account the SPIN-ORBIT interaction: n
    • Do you want to take into account the CRYSTAL FIELD effect: y
    • Please select the method to parametrize Coulomb U-matrix: 1
    • Please select method for U-interaction double counting: 12
    • Symmetrically-equivalent atom indices …: y
    • Enter up(1) dn(-1) or 0 for spin-moment of the atoms: 1
    • Is this atom correlated: y
    • Enter correlated shells: d
    • Please provide interaction parameters U,J: 7.0 0.8
    • Please provide initial guess … localized d-electrons: 6.5
    • Please select the method to solve G-RISB equations: 0
    • Please select the method to solve embedding Hamiltonian: -1

    Check the file init_ga.slog and you will see that the local self-energy structure has the following form in the single-particle basis with spin (up,down) as the faster index:

    [[1 0 0 0 0 0 0 0 0 0]
 [0 3 0 0 0 0 0 0 0 0]
 [0 0 1 0 0 0 0 0 0 0]
 [0 0 0 3 0 0 0 0 0 0]
 [0 0 0 0 1 0 0 0 0 0]
 [0 0 0 0 0 3 0 0 0 0]
 [0 0 0 0 0 0 2 0 0 0]
 [0 0 0 0 0 0 0 4 0 0]
 [0 0 0 0 0 0 0 0 2 0]
 [0 0 0 0 0 0 0 0 0 4]]

    Different integers are used for the spin-up and down conponents, inidcating spin-polarization. The self-energy is diagonal due to cubic symmetry.

    To set up the magnetic configuration, type:

    $ ${WIEN_GUTZ_ROOT2}/init_magnetism.py

    Answer the questions as follows:

    • enter spin up or down: up
    • please enter the magnitude of the field: 0.3
    • Is the external field applied only at initial step (0) …: 0

    Here we add a 0.3 eV/Bohr magneton local magnetic field to break spin symmetry INITIALLY.

  3. Type the command below to

    run the DFT+G calculation:

    $ ${WIEN_GUTZ_ROOT2}/run_ga.py

    After convergence, check the total energy in Fe.scf file, which should be close to -2540.94918 Ryd. You can also find total magnetic moment = 2.14 in the main output text file GUTZ.LOG.

  4. To plot the spin-resolved density of states

    with overall Fe-3d character, type:

    $ ${WIEN_GUTZ_ROOT2}/plot_dos_tf.py

    you will get figure as below

    alternate text
  1. To calculate the bands structure along selected k-path,

    follow the steps below:

    1. Prepare the fe.klist_band file for the high-symmetry k-path of the primitive Brillouin Zone. The SRC_templates directory of Wien2k has some examples. For instance, we can use bcc.klist file. Type the command to get the file:

      $ cp ${WIENROOT}/SRC_templates/bcc.klist Fe.klist_band

    2. Type the following command to calculate the band structure:

      $ ${WIEN_GUTZ_ROOT2}/run_ga.py -band

    3. To plot spin-resolved band structure with Fe-3d character, type:

      $ ${WIEN_GUTZ_ROOT2}/plot_band_tf.py -h # help info
$ ${WIEN_GUTZ_ROOT2}/plot_band_tf.py -el -8 -eh 10

      You will see the band structure like the following

      alternate text