[Wannier] xaxis

[Gianluca Giovannetti]

Dear All,

i`m a beginner using W90.

i`m working with FeSe.

i have the following problem to understand how the flag xaxis works in the
file ".win".

i have a unit cell in the PW simulation with two Fe (o) sites as here (+ and
- are Se sites):

Y
|    ---------------------
|    |   o1          +  |
|    |                    |
|    |                    |
|    |   -           2o |
|    ---------------------
|
|------------------------------ X

X=1,0,0
Y=0,1,0
(Z=0,0,1 is pointing out of the plane)

however i want to have printed the H(R) in the file "_hr.dat" such to have
Wannier functions of Fe states with internal reference frame directed along
the Fe-Fe bonds (then pointing along o1-----2o bonds).
Formally, if we want to maintain that e_g orbitals are x^2 - y^2 and 3z^2 -
r^2 and t_2g are xy, yz, zx then the above choice of coordinate system gives

the correct e_g - t_2g splitting coming from the Se crystal field (e_g go
lower in energy and t_2g higher).

As my hamiltonian must be written in this set, my idea would be to set
x'=1,-1,0 in the file ".win".

The output and the WFs look ok.

here the input file:

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
num_wann        = 10
num_iter        = 5000

dis_num_iter    =  500

iprint = 3

!here we exclude all bands except the O2p bands
exclude_bands : 1-16,27-50

!bands_plot_project : 1,2,3,4,5,6,7,8,9,10

write_r2mn=.true.
hr_plot=.true.

kmesh_tol=0.00001

begin atoms_cart
ang
Fe   2.82697500  0.94232500  2.74305000
Fe   0.94232500  2.82697500  2.74305000
Se   0.94232500  0.94232500  4.24459557
Se   2.82697500  2.82697500  1.24150443
end atoms_cart

begin kpoint_path
G 0.0000 0.0000 0.000 X 0.5000 0.0000 0.0000
X 0.5000 0.0000 0.000 M 0.5000 0.5000 0.000
M 0.5000 0.5000 0.000 Y 0.0000 0.5000 0.0000
Y 0.0000 0.5000 0.000 G 0.0000 0.0000 0.0000
G 0.0000 0.0000 0.000 Z 0.0000 0.0000 0.5000
end kpoint_path
bands_plot =T

!fermi_surface_plot = .true.

!To plot the WF
!wannier_plot = T
!wannier_plot_supercell = 2
!wannier_plot_list = 1 2 3 4 5 6 7 8 9 10
!restart = plot

guiding_centres = T

begin projections
Fe:dxy;dxz;dyz;dx2-y2;dz2:x=1,-1,0
end projections


begin unit_cell_cart
bohr
7.12294416914163 0.0 0.0
0.0 7.12294416914163 0.0
0.0 0.0 10.367225746512
end unit_cell_cart

mp_grid : 12 12 8

begin kpoints
(.....)
end kpoints

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------

is this correct?
do i get what i want in this way?

thank you.

Gianluca
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