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    <p>Dear Rafael González,</p>
    <p>When an integer is passed to the "bands" flag, it is interpreted
      as the <i>number</i> of bands to take into account. In your
      example</p>
    <ul>
      <li>bands=0: is equivalent to bands=[] - there are no bands to
        compute the Chern number for, which is why it doesn't work</li>
      <li>bands=1: is equivalent to bands=[0] - it computes the Chern
        number for the lower-energy bands</li>
      <li>bands=[1] computes the Chern number for the higher-energy band
        (i.e., unoccupied) band - which has the opposite value</li>
      <li>bands=[0,1] (equivalent to bands=2) - when the whole system
        (all bands) are included, it can be adiabatically connected to a
        trivial system</li>
    </ul>
    <p>I hope this helps - let me know if things are still unclear.<br>
    </p>
    <p>Best regards,</p>
    <p>Dominik<br>
    </p>
    <div class="moz-cite-prefix">On 03.08.20 20:59, Rafael Gonzalez
      Hernandez wrote:<br>
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cite="mid:CAOk20xpjmF658GDMWiomUyHJ_2ADZfaXmpZqegBwLmh+phb+-A@mail.gmail.com">
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            <div>Dear z2pack, </div>
            <div>I used the code to understand the example of Haldane
              model.</div>
            <div>However, I changed the bands flag to test it and I
              found the Chern number for different values of:</div>
            <div><br>
            </div>
            <div>band=0 chern= doesn't work</div>
            <div>band=1 chern=-1</div>
            <div>band=[0] chern=-1</div>
            <div>band=[1] chern=1</div>
            <div>band=[0,1] chern=0</div>
            <div><br>
            </div>
            <div>Why It is finding found a different between 1(both
              bands according to manual) and [0,1] bands?</div>
            <div>Thank you in advance for your help</div>
            <div><br>
            </div>
            <div>Best regards,</div>
          </div>
          -- <br>
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style="line-height:11.2pt;font-size:12pt">Rafael J. González Hernández </span></font></p>
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                                                      de Física. </span></font><font
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                                                    2-45. Bloque L-6.<br>
                                                    Tel. +57 5 3509509
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