Re: Topological invariant calculation for large system with only gamma kpoint ( No.1 ) 
 Date: 2020/07/27 11:10
 Name: Hikaru Sawahata <sawahata@cphys.s.kanazawau.ac.jp>
 Hi Frank,
Is this a Z2 invariant? Or Chern number? Or others? >The topological features
My opinion is we cannot calculate the topological invariant in most cases only Gamma point. However, only Z2 topological invariant cases, we may be able to compute it by low computational cost. Z2 invariant of the system with inversion symmetry can be evaluated by parity signs on time reversal invariant kpoints. Please see this article. https://doi.org/10.1103/PhysRevB.76.045302
Regards,
Kanazawa University Hikaru Sawahata

Re: Topological invariant calculation for large system with only gamma kpoint ( No.2 ) 
 Date: 2020/07/27 11:46
 Name: Fumiyuki Ishii
 Hi Frank
After computing SCF calculation by Gamma point, you can compute topological invariants by increasing kpoint in post processing code of computing Z2 or Chern number. Please check kpoint convergence for not SCF but post processing code.
Regards, Fumiyuki Ishii

