Regarding the value of Z2-inavriant

[Rameswar Bhattacharjee]

Dear All,
I am writing to get some suggestions on computing the value of Z2 of a
1D organic polymer.  I am getting the value 0.0 running the program
with Quantum Espresso (7.2) and Wannier90. The last two lines are as
below:

-----------------------------------------------
 Z2 topological invariant at kx = 0: 0
Z2 topological invariant at kx = 0.5: 0
-------------------------------------------

I would like to give some information about the QE set up. for
thecaluation I am using PBE with ultrasoft pseudopotential. The k
point mesh is 12*1*1. The ibrave=0 and the cell_parameters are given
in angstroms at the end. Please let me know if you want to know any
additional details.

The problem is I was expecting the value of Z2=1.0 for this system
which was reported earlier.

Therefore, my question is if there are any options to rerun the
calculation with different parameters which can  alter the  Z2 value
to 1.0 from 0.0.

Any suggestions would be highly appreciated.

thanks
Rameswar


-- 
Rameswar Bhattacharjee
Postdoctoral Scholar
Georgetown University
Washington, DC 20057