Let&#x27;s imagine a lattice like, say, this:<p><pre><code>   O--x--O--x--O ...
   |     |
   x     x
   |     |
   O--x--O--x ...
         |
         x
</code></pre>
If the x&#x27;s start jigging around, we get brief manifestations of this configuration (exaggerated):<p><pre><code>     x
    &#x2F; \
   O   O
</code></pre>
the average length of the O--x--O bond shrinks as the x&#x27;s pull away from dead center.