will have spilled over into the</span>
0139         <span class="comment">% lower half of the energy matrix (which must be upper triangular).  The next 2 steps</span>
0140         <span class="comment">% recover those values.</span>
0141         overflow = tril(interface_energy, -1);   <span class="comment">% spillover below diagonal</span>
0142         interface_energy = interface_energy + overflow' - overflow;  <span class="comment">% reflect above diagonal</span>
0143 
0144         <span class="comment">