[Wannier] Inconsistency between wannier_plot output and the Hamiltonian in the WF basis(_hr.dat)

[Fei Xue]

Dear Experts,


I have a problem with an apparent inconsistency in the signs of the Wannier
orbital W.F. I observe in the the wannier_plot routine (output in *.xsf),
compared to the the (implied) signs of the orbitals I observe in the
Hamiltonian (*_hr.dat).



The problem detail is the following:



I'm considering bcc Fe, where I use a cubic unit cell with 2 (equivalent)
atoms.  Atom1 and atom2  have positions (0,0,0) and a/2*(1,1,1),
respectively.  I project on to s, p, d atomic orbitals and do not perform
minimization of the Wannier orbital spread.  I obtain an interpolated band
structure from Wannier90 that fits the plane wave solution well.



It suffices to consider the (s, px) orbitals on atom 1 and 2.  I plot the
Wannier orbital WFs using Xcrysden.    I find that the 's' orbitals have
the same sign on both atoms, while 'px' orbitals have opposite sign on atom
1 and 2.



However, the "hopping" matrix element between these orbitals seem to reveal
that the 'px' orbitals on atom 1 and 2 have the same sign (recall they are
displaced from each other along the x-direction).  In particular:



<atom1, s | H | atom2, px >  =  +1.476

<atom2, s | H | atom1, px >  =  -1.476



found in the *_hr.dat file as:



0    0    0    1   12    1.476361    0.000002

0    0    0   10    3   -1.476345    0.000003



This pattern of signs for the hopping is inconsistent with the signs of the
wannier orbitals I observe using XCrysDen



This leads to the question: can the output of the code for the Hamiltonian
use different signs for the orbitals compared to the output of the code for
the real space orbitals?



The wannier90 input file is:


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

num_bands         =   50

num_wann          =   18

spin = up

bands_plot = true

wannier_plot = true

wannier_plot_supercell = 5

#dis_win_max       = 85d0

dis_froz_max      =  30d0

dis_num_iter      =  0

num_iter          = 1000

dis_mix_ratio = 1

write_hr = true



begin atoms_frac

Fe 0.0 0.0 0.0

Fe 0.5 0.5 0.5

end atoms_frac



begin unit_cell_cart

Bohr

5.4235 0. 0.

0. 5.4235 0.

0. 0. 5.4235

end unit_cell_cart



begin projections

f = 0., 0., 0.: s;p;d

f = 0.5, 0.5, 0.5: s;p;d

end projections



bands_num_points = 100



begin kpoint_path

G 0.0000 0.0000 0.0000  H 0.500 -0.5000 -0.5000

H 0.500 -0.5000 -0.5000 P 0.7500 0.2500 -0.2500

P 0.7500 0.2500 -0.2500 N 0.5000 0.0000 -0.5000

end kpoint_path



mp_grid      = 8 8 8



begin kpoints

  0.00000000  0.00000000  0.00000000

  0.00000000  0.00000000  0.12500000

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

Best

Fei

-- 

Dr. Fei Xue

Postdoctoral Research Associate

University of Maryland/National Institute of Standards and Technology

100 Bureau Dr. Stop 8412

RM B231, Bldg. 216

Gaithersburg, MD 20899-8412

Phone: (301) 975-4360

Work Email: fei.xue at nist.gov

Permanent Email: feixue at utexas.edu
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