Hi Matthias,<div><br></div><div>Thanks for your reply. Below is the simplest implementation that I could cook up with free spinless fermions on two sites with *directed* bonds. The output of sparsediag, including the error, is </div>
<div>--------------------------------------------------------------------------</div><div><div>parsing task files ... </div><div>Starting task 1.</div><div>Quantumnumber N going from 0 to 2 with increment 1</div><div>Cannot evaluate expression t# * 1 * 1</div>
</div><div>--------------------------------------------------------------------------</div><div><br></div><div>My short source is attached below. I hope that it&#39;s a quick task to figure out what is wrong with the implementation.</div>
<div><br></div><div>Thanks in advance,</div><div>Alex</div><div><br></div><div>Alexandru Petrescu / Physics Department, Yale University</div><div><br></div><div><br></div><div>Code attachment</div><div><br></div><div>In &lt;alps-dir&gt;/lib/xml/lattices.xml I added</div>
<div>------------------------------------------------------------------------</div><div>&lt;GRAPH name=&quot;my 2-site&quot; vertices=&quot;2&quot;&gt;</div><div><div>  &lt;EDGE source=&quot;1&quot; target=&quot;2&quot; type=&quot;1&quot;/&gt;</div>
<div>  &lt;EDGE source=&quot;2&quot; target=&quot;1&quot; type=&quot;2&quot;/&gt;</div><div>&lt;/GRAPH&gt;</div></div><div>-------------------------------------------------------------------------</div><div><br></div><div>
In &lt;alps-dir&gt;/lib/xml/models.xml,</div><div>------------------------------------------------------------------------</div><div><div>&lt;HAMILTONIAN name=&quot;free spinless fermions with bondterm type&quot;&gt;</div>
<div>  &lt;PARAMETER name=&quot;mu&quot; default=&quot;0&quot;/&gt;</div><div>  &lt;PARAMETER name=&quot;t&quot; default=&quot;1&quot;/&gt;</div><div>  &lt;BASIS ref=&quot;spinless fermion&quot;/&gt;</div><div>  &lt;SITETERM site=&quot;i&quot;&gt;</div>
<div>    &lt;PARAMETER name=&quot;mu#&quot; default=&quot;mu&quot;/&gt;                                             </div><div>    -mu#*n(i)                                                                        </div><div>
  &lt;/SITETERM&gt;</div><div>  &lt;BONDTERM type=&quot;1&quot;  source=&quot;i&quot; target=&quot;j&quot;&gt;</div><div>    &lt;PARAMETER name=&quot;t#&quot; default=&quot;t&quot;/&gt;</div><div>    -t#*(cdag(i)*c(j)+cdag(j)*c(i))                                                  </div>
<div>  &lt;/BONDTERM&gt;</div><div><div>  &lt;BONDTERM type=&quot;2&quot;  source=&quot;i&quot; target=&quot;j&quot;&gt;</div><div>    &lt;PARAMETER name=&quot;t#&quot; default=&quot;t&quot;/&gt;</div><div>    -t#*(cdag(i)*c(j)+cdag(j)*c(i))                                                  </div>
<div>  &lt;/BONDTERM&gt;</div></div><div>&lt;/HAMILTONIAN&gt;</div></div><div>-------------------------------------------------------------------------</div><div>The parameter file is</div><div><div><br></div><div>LATTICE=&quot;my 2-site&quot;;</div>
<div>-------------------------------------------------------------------------</div><div>MODEL=&quot;free spinless fermions with bondterm type&quot;</div><div>NUMBER_EIGENVALUES = 1</div><div>CONSERVED_QUANTUMNUMBERS=&quot;N&quot;</div>
<div>MEASURE_ENERGY = true</div><div><br></div><div>t<span class="Apple-tab-span" style="white-space:pre">	</span>= 3.0;</div><div>V      = 0.0;</div><div><br></div><div>{mu=0.00}</div></div><div>--------------------------------------------------------------------------</div>
<div><br></div><div>If instead &quot;spinless fermions&quot; with V=0 are used in the parameter file, sparsediag works, but all energies come out to be 0. </div>