ed_matrix</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">zeros</span><span class="p">((</span><span class="n">n_atoms</span><span class="p">,</span> <span class="n">n_atoms</span><span class="p">))</span>

    <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">n_atoms</span><span class="p">):</span>
        <span class="k">for</span> <span class="n">j</span> <spa