Dear ALPS developers,<br>Thank you for your quick and very helpful reply.<br>I might be doing something wrong as is the first time I define a lattice in ALPS by myself.<br>I want to add to the Heisenberg Hamiltonian on a 1d spin chain the term<div>
<br></div><div>Sz(i)*Sz(i+2)<br><br>In the lattice file I set the basis as<br><br> &lt;BASIS&gt;&lt;VECTOR&gt;1&lt;/VECTOR&gt;&lt;/BASIS&gt;<br><br>and in the unit cell I put the two bonds <br><br>&lt;EDGE type=&quot;0&quot;&gt;&lt;SOURCE vertex=&quot;1&quot; offset=&quot;0&quot;/&gt;&lt;TARGET vertex=&quot;1&quot; offset=&quot;1&quot;/&gt;&lt;/EDGE&gt;<br>

  &lt;EDGE type=&quot;1&quot;&gt;&lt;SOURCE vertex=&quot;1&quot; offset=&quot;0&quot;/&gt;&lt;TARGET vertex=&quot;1&quot; offset=&quot;2&quot;/&gt;&lt;/EDGE&gt;<br><br>which, as far I have understood connect respectively sites 1, and 2 lattice spacing far.<br>

Then in the model file I define the bond operators as</div><div><div><br></div><div>&lt;BONDOPERATOR type=&quot;0&quot; name=&quot;usual&quot; source=&quot;x&quot; target=&quot;y&quot;&gt;</div><div>   usual Heisenberg bond term...</div>
<div> &lt;/BONDOPERATOR&gt;  </div></div><div><div>&lt;BONDOPERATOR type=&quot;1&quot; name=&quot;test&quot; source=&quot;x&quot; target=&quot;y&quot;&gt;</div><div>   Sz(x)*Sz(y)</div><div> &lt;/BONDOPERATOR&gt;  </div><div>
<br></div><div><br></div><div>and I put them in the Hamiltonian as</div><div><br></div><div><div> &lt;BONDTERM type=&quot;0&quot; source=&quot;i&quot; target=&quot;j&quot;&gt;</div><div>       usual(i,j)</div><div>   &lt;/BONDTERM&gt;</div>
<div>   &lt;BONDTERM type=&quot;1&quot; source=&quot;i&quot; target=&quot;j&quot;&gt;</div><div>      Jtest*test(i,j)</div><div>   &lt;/BONDTERM&gt;</div></div><div><br></div><div>But it gives me error. It creates the parameter file but doesn&#39;t manage to compute any simulations (fulldiag, dmrg, etc etc).</div>
<div>I think is the way I have written it that has something wrong. Moreover I don&#39;t manage to use printgraph in any way to see if the lattice is correct. Do I have to use printgraph on the xml lattice file?</div><div>
<br></div><div>Many thanks in advance for your help.</div><div>Kindest regards.</div><div> </div>-- <br>Emanuele Levi<br><br><a href="mailto:emanuele.levi@gmail.com" target="_blank">emanuele.levi@gmail.com</a><br><br><br>

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