[Wannier] How to use wannier-kslice-curv to calculate chern number

[杨晟祺]

I am computing the berry curvature and chern number of a 2D material.
Below is part of my wannier.win:
#berry=true
#berry_task=ahc
#berry_kmesh=25 25 1
fermi_energy=-2.423600000000
berry_curv_unit=ang2

kpath=false
#kpath_task=bands+curv
#kpath_bands_colour=spin
#kpath_num_points=1000

kslice=true
kslice_task=curv+fermi_lines
kslice_corner=0.0 0.0 0.0
kslice_b1=1.0 0.0 0.0
kslice_b2=0.0 1.0 0.0 
kslice_2dkmesh=200 200

Below is part of the wannier.wpout:
                                    ------
                                    SYSTEM
                                    ------
 
                              Lattice Vectors (Ang)
                    a_1     5.767388   0.000000   0.000000
                    a_2    -2.883694   4.994704   0.000000
                    a_3     0.000000   0.000000  14.349700
 
                   Unit Cell Volume:     413.36313  (Ang^3)
 
                        Reciprocal-Space Vectors (Ang^-1)
                    b_1     1.089434   0.628985   0.000000
                    b_2     0.000000   1.257969   0.000000
                    b_3     0.000000   0.000000   0.437862

After running postw90, I get wannier-kslice-curv.dat. I believe the three rows in this file is berry curvature on x,y,z direction respectively. According to the definition of Chern number, C=(SumCurv*Sbz)/(kmesh1*kmesh2*2*pi),where SunCurv is the sum of all berry curvature in certain row. Sbz is the area of the first BZ, kmesh1*kmesh2 is the multiplication of the two number in kslice_2dkmesh. However, I cannot get an integer. This material is an insulator so its chern number must be an integer.  

I sumed all data in each row of wannier-kslice-curv.dat and below is the result.
berry =

  1.0e+003 *

    0.0004    0.0010   -3.9866

Chern number of this system should be -2. Does anyone know how to compute chern number with wannier90? 
Thank you very much for your help!
--
Department of Physics, Fudan University
Shengqi Yang
Tel: (+86)18817873184