[Pw_forum] Use of wannier90.x for the calculation of Born Effective Charge

[yukihiro_okuno at fujifilm.co.jp]

Dear PWSCF users.

I'm now using wannier90.x in PWSCF package (espresso-4.1) for

the calculation of Born Effective charge for each orbital like

N.Marzari and D. Vanderbilt  http:/arxiv.org/abs/cond-mat/9802210.

I employ the example of BaTiO3.

For cubic symmetry (centro symmetric atomic position),  the calculation

is done with reasonable results.   But, in order to calculate

the Ti's Born effective charge ,   I displacing the Ti atom, like ( 0.5 0.5
0.505) from

the centro-symmetric position (0.5,0.5,0.5),  the error occurred in the

calculation of pw2wannier.x  with the message below,

Something wrong

numk = 64    iknum=  130.


This is due to that the symmetry is lowered by the displacement of Ti atom

and the k-points are  added in the non-SCF calculation

in PWSCF (in the subroutine sgama).


If we set nosym in the input file of non-SCF calculation with k-points is
same as

BaTiO3.win file., the symmetry of the results of wannier center

broken, so the calculated Born Effective Charges are wrong.

How should treat the k-points inconsistent when we calculate the Born
effective

charge in displacing the atom.

Here is my input file for BaTiO3.win.


num_wann        =  9
num_iter        = 100

!here we exclude all bands except the O2p bands
exclude_bands : 1,2,3,4,5,6,7,8,9,10,11

write_xyz = T
guiding_centres = T

begin atoms_frac
Ba 0.0 0.0 0.0
Ti 0.5 0.5 0.502
O  0.0 0.5 0.5
O  0.5 0.5 0.0
O  0.5 0.0 0.5
end atoms_frac

begin kpoint_path
L 0.50000  0.50000 0.5000 G 0.00000  0.00000 0.0000
G 0.00000  0.00000 0.0000 X 0.50000  0.00000 0.5000
X 0.50000 -0.50000 0.0000 K 0.37500 -0.37500 0.0000
K 0.37500 -0.37500 0.0000 G 0.00000  0.00000 0.0000
end kpoint_path
bands_plot =T


!!To plot the WF
!restart = plot
!wannier_plot = true
!wannier_plot_supercell = 2
!wannier_plot_list = 3


begin projections
O:p
end projections


begin unit_cell_cart
bohr
7.44266 0.0 0.0
0.0 7.44266 0.0
0.0 0.0 7.44266
end unit_cell_cart

mp_grid : 4 4 4

begin kpoints
  0.00000000  0.00000000  0.00000000
  0.00000000  0.00000000  0.25000000
  0.00000000  0.00000000  0.50000000
  0.00000000  0.00000000  0.75000000
  0.00000000  0.25000000  0.00000000
  0.00000000  0.25000000  0.25000000
  0.00000000  0.25000000  0.50000000
  0.00000000  0.25000000  0.75000000
  0.00000000  0.50000000  0.00000000
  0.00000000  0.50000000  0.25000000
  0.00000000  0.50000000  0.50000000
  0.00000000  0.50000000  0.75000000
  0.00000000  0.75000000  0.00000000
  0.00000000  0.75000000  0.25000000
  0.00000000  0.75000000  0.50000000
  0.00000000  0.75000000  0.75000000
  0.25000000  0.00000000  0.00000000
  0.25000000  0.00000000  0.25000000
  0.25000000  0.00000000  0.50000000
  0.25000000  0.00000000  0.75000000
  0.25000000  0.25000000  0.00000000
  0.25000000  0.25000000  0.25000000
  0.25000000  0.25000000  0.50000000
  0.25000000  0.25000000  0.75000000
  0.25000000  0.50000000  0.00000000
  0.25000000  0.50000000  0.25000000
  0.25000000  0.50000000  0.50000000
  0.25000000  0.50000000  0.75000000
  0.25000000  0.75000000  0.00000000
  0.25000000  0.75000000  0.25000000
  0.25000000  0.75000000  0.50000000
  0.25000000  0.75000000  0.75000000
  0.50000000  0.00000000  0.00000000
  0.50000000  0.00000000  0.25000000
  0.50000000  0.00000000  0.50000000
  0.50000000  0.00000000  0.75000000
  0.50000000  0.25000000  0.00000000
  0.50000000  0.25000000  0.25000000
  0.50000000  0.25000000  0.50000000
  0.50000000  0.25000000  0.75000000
  0.50000000  0.50000000  0.00000000
  0.50000000  0.50000000  0.25000000
  0.50000000  0.50000000  0.50000000
  0.50000000  0.50000000  0.75000000
  0.50000000  0.75000000  0.00000000
  0.50000000  0.75000000  0.25000000
  0.50000000  0.75000000  0.50000000
  0.50000000  0.75000000  0.75000000
  0.75000000  0.00000000  0.00000000
  0.75000000  0.00000000  0.25000000
  0.75000000  0.00000000  0.50000000
  0.75000000  0.00000000  0.75000000
  0.75000000  0.25000000  0.00000000
  0.75000000  0.25000000  0.25000000
  0.75000000  0.25000000  0.50000000
  0.75000000  0.25000000  0.75000000
  0.75000000  0.50000000  0.00000000
  0.75000000  0.50000000  0.25000000
  0.75000000  0.50000000  0.50000000
  0.75000000  0.50000000  0.75000000
  0.75000000  0.75000000  0.00000000
  0.75000000  0.75000000  0.25000000
  0.75000000  0.75000000  0.50000000
  0.75000000  0.75000000  0.75000000
end kpoints



Sincerely.