NiO Wannier90 example

3 minute read

This is the example of a G-type ordered NiO with Wannier90. In the primitive cell, two spins have different up, down the order. After the Wannier Hamiltonian is constructed, the MFT calculation procedures consist of two-step processes of calculating J(q) and converting J(q) to J(R).

Before MFT calculation, it is STRONGLY recommended to compare the Wannier band with the original DFT band structure. Especially for the metallic systems, a small difference near the Fermi level could significantly impact linear response calculations.

The required files for Jx MFT calculation (with Wannier90)

The required files for MFT calculation: Wannier90 Hamiltonian files and toml input files.

The important tasks are to write feremi_energy in Wannier90 info and the number of atoms, atom position, and orbital info in the input toml file. Use ‘grep fermi OUTCAR’.

J(q) calculation

cd examples/NiO_G_AFM.Wannier90.example

julia -p 4 src/Jx_col_spin_exchange.jl  -T nio_J_wannier90.toml

This is the main MFT procedure. This is the most time-consuming part. For MFT with Wannier Hamiltonians, the output path is jx2.col.spin.wannier_0.0 (not jx2.col.spin_0.0), and inside the output path following files jx2.col.spin.wannier_wannier90_atomij_1_1_atom1m_[,]_atom2m_[,]_[eg_eg__all__all]_ChemPdelta_0.0.jld2, jx2.col.spin.wannier_wannier90_atomij_1_1_atom1m_[,]_atom2m_[,]_[eg_t2g__all__all]_ChemPdelta_0.0.jld2, jx2.col.spin.wannier_wannier90_atomij_1_1_atom1m_[,]_atom2m_[,]_[t2g_eg__all__all]_ChemPdelta_0.0.jld2, jx2.col.spin.wannier_wannier90_atomij_1_1_atom1m_[,]_atom2m_[,]_[t2g_t2g__all__all]_ChemPdelta_0.0.jld2, jx2.col.spin.wannier_wannier90_atomij_1_2_atom1m_[,]_atom2m_[,]_[eg_eg__all__all]_ChemPdelta_0.0.jld2, jx2.col.spin.wannier_wannier90_atomij_1_2_atom1m_[,]_atom2m_[,]_[eg_t2g__all__all]_ChemPdelta_0.0.jld2, jx2.col.spin.wannier_wannier90_atomij_1_2_atom1m_[,]_atom2m_[,]_[t2g_eg__all__all]_ChemPdelta_0.0.jld2, jx2.col.spin.wannier_wannier90_atomij_1_2_atom1m_[,]_atom2m_[,]_[t2g_t2g__all__all]_ChemPdelta_0.0.jld2 will be generated.

The parallel option can be given by -p #of cpu core or --machine-file #PBS_NODES. See Julia parallel computing for detailed options.

J(q)->J(R) transformation

julia  src/Jx_postprocess.jl --cellvectors  2_2_2 --baseatom 1 --atom2 1,2 --orbital_name eg_eg  jx2.col.spin.wannier_0.0

The output files are jx2.col.spin.wannier_wannier90_atomij_1_1_atom1m_[,]_atom2m_[,]_[eg_eg__all__all]_ChemPdelta_0.0.csv jx2.col.spin.wannier_wannier90_atomij_1_2_atom1m_[,]_atom2m_[,]_[eg_eg__all__all]_ChemPdelta_0.0.csv and the ploted image Jplot_1_1,2_eg_eg.pdf.

Note that the raw sign of the MFT results contains information about whether a system likes or dislikes the current spin order. So, at the second nearest (4.18 Å) between 1-2 spins, +12 meV means that current antiferromagnetic ordering is preferred.

The other orbitals interaction can be plotted by changing orbital_name options as follows --orbital_name eg_t2g, --orbital_name t2g_t2g, --orbital_name t2g_eg.

The files provided in the example

Wannier90 infofile

  • The fermi_energy MUST be set for BOTH wannier90.1.win and wannier90.2.win files from the DFT results. Users can find it by grep fermi OUTCAR.
###### Energy windows #########
  dis_win_min = -1
  dis_win_max = 10
  dis_froz_min = -1
  dis_froz_max = 6
###############################

######### Wannierizing ########
  dis_num_iter    = 10000


######### Projections ########
  begin projections
  f= 0.000, 0.000, 0.000:d
  f=-0.500,-0.500,-0.500:d
  f= 0.250, 0.250, 0.250:p
  f=-0.250,-0.250,-0.250:p
  end projections


#########################################
# Band Plots
#########################################

  bands_plot = T
  begin kpoint_path
   Z' 0.0000 0.0000  0.5000   Y  0.0000  0.5000   0.0000
   Y  0.0000 0.5000  0.0000   X  0.5000  0.0000   0.0000
   X  0.5000 0.0000  0.0000   G  0.0000  0.0000   0.0000
   G  0.0000 0.0000  0.0000   Z  0.5000  0.5000   0.5000
   Z  0.5000 0.5000  0.5000   K  0.8125  0.34375  0.34375
   K  0.8125 0.34375 0.34375  U  0.1875 -0.34375 -0.34375
  end kpoint_path
  bands_num_points 20

###### writing hamiltonian ######
  WRITE_HR = True
###############################

###### fermi energy  ##########
  fermi_energy =  8.7042
###############################

nio_J_wannier90.toml

  • The atomnum, atompos, atoms_orbitals_list must be updated for each different system.
HamiltonianType = "Wannier90"
spintype = "co_spin"        #Set Spin type, para, co_spin, nc_spin

# wannier90.up.win, wannier90.up_hr.dat // wannier90.dn.win, wannier90.dn_hr.dat files are required.
result_file = ["wannier90.1","wannier90.2"]

atom12 = [[1,1],[1,2]]


k_point_num = [8,8,8]
q_point_num = [8,8,8]

[orbitals]
orbitalselection = true # true , false
orbital_mask1_list = [[1,4],[2,3,5]]
orbital_mask2_list = [[1,4],[2,3,5]]

orbital_mask1_names = "[eg,t2g]"
orbital_mask2_names = "[eg,t2g]"

# For d-orbital index see
# http://www.wannier.org/doc/user_guide.pdf
#orbital_mask1_list = [[1],[2],[3],[4],[5]]
#orbital_mask2_list = [[1],[2],[3],[4],[5]]

#orbital_mask1_names = "[dz2,dxz,dyz,dx2y2,dxy]"
#orbital_mask2_names = "[dz2,dxz,dyz,dx2y2,dxy]"

[wannier_optional]
# atom position info dose not exists at wannier
# atompos in fractional coordinate
# Please check the atomic position through .wout
atomnum = 4
atompos = [[   0.0,    0.0,  0.0  ],       # atom1 Ni1
           [  -0.5,   -0.5, -0.5  ],       # atom2 Ni2
           [ 0.250,  0.250,  0.250],       # atom3 O1
           [-0.250, -0.250, -0.250] ]      # atom4 O2

# orbital indexes for each atoms
atoms_orbitals_list = [[1,2,3,4,5], # atom1 Ni1
                [6,7,8,9,10],       # atom2 Ni2
                [11,12,13],         # atom3 O1
                [14,15,16]]         # atom4 O2