This program calculates the parity of each band at the TR kpts and determines the Z2 index using the parity method using PRB 76, 045302 (2007) Requirement: 1. SCF calculation with SOC 2. NSCF calculation with SOC using 8 TR kpts explicitly 3. Both above MUST use wf_collect=.true. 4. cd into the .save directory and run this program with a single parameter of the number of filled bands Possible caveats: 1. No checks (assuming you follow the previous 4 steps strictly) 2. For USPP & PAWs, one indeed needs <psi_i|P S|psi_i> where S is the projection S=1+Q_ij |beta_i><beta_j|, but since this is nothing but a parity calculation, so I did not bother.
Author: Chao Cao @ Hangzhou Normal University (2015) (ccao1981@gmail.com)