Dear Rafael González,

When an integer is passed to the "bands" flag, it is interpreted as the number of bands to take into account. In your example

• bands=0: is equivalent to bands=[] - there are no bands to compute the Chern number for, which is why it doesn't work
• bands=1: is equivalent to bands=[0] - it computes the Chern number for the lower-energy bands
• bands=[1] computes the Chern number for the higher-energy band (i.e., unoccupied) band - which has the opposite value
• bands=[0,1] (equivalent to bands=2) - when the whole system (all bands) are included, it can be adiabatically connected to a trivial system

I hope this helps - let me know if things are still unclear.

Best regards,

Dominik

Dear z2pack, 

I used the code to understand the example of Haldane model.

However, I changed the bands flag to test it and I found the Chern number for different values of:

band=0 chern= doesn't work

band=1 chern=-1

band=[0] chern=-1

band=[1] chern=1

band=[0,1] chern=0

Why It is finding found a different between 1(both bands according to manual) and [0,1] bands?

Thank you in advance for your help

Best regards,

--

Rafael J. González Hernández  Profesor Asociado  Departamento de Física. Of. 2-45. Bloque L-6. Tel. +57 5 3509509  Ext. 3425  Email: rhernandezj@uninorte.edu.co

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