pan>
0133         interface_energy(first,:) = interface_energy(first,:) + interface_energy(second,:);
0134         interface_energy(second,:) = 0;
0135         interface_energy(:,first) = interface_energy(:,first) + interface_energy(:,second);
0136         interface_energy(:,second) = 0;
0137         interface_energy(second,second) = 1;  <span class="comment">% keep self-energy at 1 (we may divide by it later)</span>
0138         <span class="comment">% since we added rows &amp; columns, some energy values 