                from 1 to nelements, assigning an element to each atom in the</span>
<span class="sd">                  system</span>
<span class="sd">                - elements (size natom list): a vector of element names</span>
<span class="sd">                - positions (size natomx3 array): atomic positions in lattice</span>
<span class="sd">                  coordinates</span>
<span class="sd">                - scell (size 3 list): supercell sizes along each crystal axis</span>
<span class="sd">      